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Civic Report
 No. 53 May 2008

Measuring Immigrant Assimilation in the United States

by Jacob L. Vigdor

Executive Summary

This report introduces a quantitative index that measures the degree of similarity between native- and foreign-born adults in the United States. It is the ability to distinguish the latter group from the former that we mean when we use the term “assimilation.” The Index of Immigrant Assimilation relies on Census Bureau data available in some form since 1900 and as current as the year before last. The index reveals great diversity in the experiences of individual immigrant groups, which differ from each other almost as much as they differ from the native-born. They vary significantly in the extent to which their earnings have increased, their rate of learning the English language, and progress toward citizenship. Mexican immigrants, the largest group and the focus of most current immigration policy debates, have assimilated slowly, but their experience is not representative of the entire immigrant population.

Collective assimilation rates are lower than they were a century ago, although no lower than they have been in recent decades. And this is true despite the fact that recent immigrants have arrived less assimilated than their predecessors and in very large numbers. In addition to country of origin, the Index categorizes groups on the basis of date of arrival, age, and place of residence. Some groups have done far better or worse than the Index as a whole; Assimilation also varies considerably across metropolitan areas.

Here are some of the Index's significant findings:

  • The degree of similarity between the native- and foreign-born, although low by historical standards, has held steady since 1990. Assimilation declined during the 1980s, remained stable through the 1990s, and has actually increased slightly over the past few years.

Beyond presenting a snapshot of the degree of similarity between the native- and foreign-born, the assimilation index can be used to track the progress of immigrants who arrived in the United States at a common point in time. This simple extension shows that the relative stability of immigrant assimilation since 1990 masks two important and countervailing trends.

  • Newly arrived immigrants of the early 21st century have assimilation index values lower than the newly arrived immigrants of the early 20th century. Growth in the immigrant population usually lowers the assimilation index because newly arrived immigrants drag down the average for the group as a whole. This phenomenon can be seen between 1900 and 1920 and again in the 1980s. The stability of the assimilation index since 1990 is therefore remarkable in light of the rapid growth of the immigrant population, which doubled between 1990 and 2006.
  • Immigrants of the past quarter-century have assimilated more rapidly than their counterparts of a century ago, even though they are more distinct from the native population upon arrival. The increase in the rate of assimilation among recently arrived immigrants explains why the overall index has remained stable, even though the immigrant population has grown rapidly.
  • Yet the current level of assimilation remains lower than it was at any point during the early 20th century wave of immigration.

The assimilation index can be decomposed along several other dimensions. The overall, or composite, index is based on a series of economic, cultural, and civic factors. These sets of factors can be examined in isolation to produce three component indices. The economic index compares the labor force, educational attainment, and home ownership patterns of the foreign- and native-born. The cultural index focuses on English-speaking ability, marriage, and childbearing patterns. The civic index examines naturalization rates and compares the military service patterns of the foreign- and native-born. Separate analysis of these three dimensions of assimilation reveals that they do not increase in lockstep as immigrants spend more time in the United States.

  • Economic and civic assimilation often occurs without significant cultural assimilation. It is common for immigrant cohorts to naturalize and enjoy integration into the economic mainstream without posting many gains along cultural dimensions.
  • Immigrants who arrived in the United States after 1995 are culturally assimilating more rapidly than their predecessors. The increased rate of overall assimilation shown by cohorts of recent arrivals can be traced in part to this pattern of relatively rapid cultural assimilation.

The assimilation index can be computed for individual country-of-origin groups, or for sets of immigrants who live in a particular city or region. Disaggregation by country of origin reveals important differences in the experiences of immigrants born in different parts of the world.

  • Immigrants from developed countries are not necessarily more assimilated. Immigrants born in Korea, which the World Bank classifies as a high-income country, have a collective assimilation index value lower than that of immigrants from Cuba or the Philippines, which are classified as low-income countries. Several factors can explain this pattern, among them the fact that immigrants from developed countries do not necessarily become naturalized citizens more rapidly than those from the developing world. The United States often attracts immigrants who belonged to the economic elite of their origin country.
  • Immigrants from Vietnam, Cuba, and the Philippines enjoy some of the highest rates of assimilation. However, these groups assimilate more rapidly in some respects than others. For example, they are far more assimilated economically than they are culturally. Curiously, all of the countries mentioned have experienced U.S. military occupation.
  • Mexican immigrants experience very low rates of economic and civic assimilation. Immigrants born in Mexico, particularly those living and working in the United States illegally, lie at the heart of many current debates over immigration policy. The assimilation index shows that immigrants from Mexico are very distinct from the native-born upon arrival and assimilate slowly over time. The slow rates of economic and civic assimilation set Mexicans apart from other immigrants, and may reflect the fact that the large numbers of Mexican immigrants residing in the United States illegally have few opportunities to advance themselves along these dimensions.
  • Mexican immigrants experience relatively normal rates of cultural assimilation. Recent cohorts of Mexican immigrants have increased their rate of cultural assimilation just as immigrants born in other nations have done.

A specialized version of the assimilation index can be computed for foreign-born adolescents and young adults who came to the United States as young children and received their formal education exclusively in this country. This version of the assimilation index also reveals interesting patterns.

  • The foreign-born children of immigrants continue to bear a strong resemblance to their native-born counterparts. Although many members of this group are not naturalized citizens, they are difficult to distinguish from the native-born along other dimensions.
  • Immigrant children born in Mexico are more distinct than immigrant children born in other foreign nations. This distinction is most obvious in terms of comparative naturalization rates, but extends to other dimensions as well. Mexican adolescents are imprisoned at rates approximately 80 percent greater than immigrant adolescents generally.
  • Naturalization rates among the foreign-born children of immigrants have been increasing. In this respect, the behavior of foreign-born, domestically educated immigrants resembles that of their parents educated abroad.

Disaggregation by metropolitan area reveals widely varying rates of assimilation, due largely to the different combinations of immigrant groups that reside in each and the different characteristics of those groups.

  • Polyethnic New York City, which still attracts large numbers of European immigrants, has the second-highest assimilation index value among the metropolitan areas defined.
  • San Diego, despite its proximity to the Mexican border, has the highest.

The methodology used to compute the assimilation index is outlined in the report and reviewed extensively in a more technical appendix. The method has been designed to take advantage of more than a century’s worth of historical data on the status of immigrants in the United States, made available to the public by the United States Census Bureau, and to provide the opportunity for annual updates.

The assimilation index points to marks of success, to encouraging recent trends, and also to areas of concern. Within these areas of concern, the index provides some insight into the nature of the problem and the universe of appropriate potential policy responses. It is important to note, however, that this report neither proposes nor endorses any policy responses. Its sole purpose is to present information in a manner useful to concerned citizens and policymakers who hope to make informed decisions regarding the proper course of action.


About the Author

Jacob Vigdor is Associate Professor of Public Policy Studies and Economics at Duke University, where he has taught since 1999, and a Faculty Research Fellow at the National Bureau of Economic Research. He received a B.S. in Policy Analysis from Cornell University in 1994 and a Ph.D. in Economics from Harvard University in 1999.

His research interests are in the broad areas of education policy, housing policy, and political economy. Within those areas, he has published numerous scholarly articles on the topics of residential segregation, immigration, housing affordability, the consequences of gentrification, the determinants of student achievement in elementary school, the causes and consequences of delinquent behavior among adolescents, teacher turnover, civic participation and voting patterns, and racial inequality in the labor market. These articles have been published in outlets such as The Journal of Political Economy, The Review of Economics and Statistics, The Journal of Public Economics, The Journal of Human Resources, and The Journal of Policy Analysis and Management.

1. Introduction

The immigrant population of the United States has nearly quadrupled since 1970, and doubled since 1990. This remarkable growth, plotted in Figure 1, has been driven in large part by immigration from Latin America and Asia.[1] The immigrant population has grown at more than twice the rate of the population as a whole. Recent Census Bureau estimates indicate that there are more than 10 million Mexican-born individuals currently residing in the United States. The number of immigrants from this one country today exceeds the total number of immigrants from all nations little more than a generation ago. Moreover, a considerable portion of Mexican-born residents of the United States are undocumented, living and working in violation of the law. A study released by the Census Bureau in 2001 indicates that there were nearly 9 million immigrants from all countries who did not fall into an “officially estimated” legal category at that time. Nearly half of these immigrants of questionable legal status were from Mexico.[2]

This remarkable growth has been accompanied by continued and escalating calls to reform immigration policy not only at the national level but within large and small communities across the country. Immigration policy debates touch on a wide array of arguments: economic, political, ethical, legal, and emotional. In many cases, these debates are also influenced by incomplete or misleading information. All sides in the debate face a trade-off between conveying a concise message and oversimplifying an inherently complex issue.

The purpose of this report is to present information relevant to these ongoing debates by measuring the degree of distinction between the native- and foreign-born populations of the United States, or alternatively, their degree of assimilation.[3] The analysis introduces a numeric index of assimilation, which measures the extent to which the foreign-born and native-born can be distinguished from each other on the basis of commonly observed social and economic data. The index measures the ability of a statistical algorithm to predict which individuals in a random sample of United States residents were born abroad. An appendix to this report provides both a general and a more technical overview of the method used to compute the index. The index can be computed for individual country-of-origin groups, sets of immigrants residing in specific cities or regions, and for immigrants who have spent varying lengths of time in the United States. The index, which makes use of data provided by the Census Bureau, can be computed using data capturing conditions as recent as 2006, and as distant as 1900. The index can serve to answer two simple but important questions: Are the differences between immigrants and natives today larger than they were in the recent or distant past? And how rapidly do these differences shrink as immigrants spend more time in the United States?

The study of immigrant assimilation is not new, nor is it in a period of dormancy. Past studies of immigrant assimilation range from detailed observation of particular immigrant enclaves to broader statistical analyses of nationally representative samples.[4] The observational studies provide rich detail on the habits and interpersonal connections of actual people but can be criticized on the grounds that they don’t permit generalization about an entire population of immigrants. The broader statistical analyses are easily generalized but often focus on a limited set of measures, the most prominent ones being earnings and other labor-force outcomes, English-speaking ability, naturalization, and intermarriage.

The assimilation index builds on this previous literature by using broad, nationally representative samples that include native-born Americans and by analyzing a wider array of measures. The index summarizes this large quantity of information in a form that can be applied to very broad and very narrow groups of immigrants. The method requires no prior assumptions regarding which characteristics are most effective in distinguishing immigrants from natives. Moreover, the inclusion of irrelevant characteristics—that is, ones that do not actually help distinguish immigrants from natives—has no impact on the index.

The social and economic data used to compute the overall, or composite, assimilation index can be separated into three sets of factors, which in turn can be used in isolation to compute more narrowly focused component indexes:

Economic assimilation describes the extent to which immigrants, or groups of immigrants, make productive contributions to society indistinguishable in aggregate from the contributions of the native-born. Economic assimilation is low when immigrants cluster at certain points on the economic ladder—most notably, the low-skilled rungs—and high when their distribution on the economic ladder matches that of native-born Americans.

The economic assimilation index is particularly relevant to two major areas of policy debate: the impact of immigration on the labor market; and the fiscal impact of immigration. A simple calculation suggests that immigrant participation in the labor market generates net benefits, through lower consumer prices and higher shareholder returns, of $50 billion per year.[5] But such benefits are accompanied by reductions in wages for native workers competing in the same market.[6] It has also been argued that the immigration of highly skilled, entrepreneurial workers creates new jobs.[7] The economic assimilation index can help track whether the skills of immigrants are matched to or mismatched with those of native workers.

From a fiscal perspective,[8] the economic assimilation index reveals information that can potentially address concerns that immigrants take up welfare benefits at disproportionate rates[9] or rely on charitable provision of health care.[10] Economic assimilation also correlates with immigrants’ contributions to the Social Security and Medicare trust funds[11] and may help determine the impact of immigrants’ housing demand on property values and local property tax revenues.[12]
The following factors are used to measure economic assimilation:

• Earned income in the year prior to the survey (not available for 1900–1930)
• Labor-force participation
• Unemployment (not available for 1900–1930)
• A quantitative ranking of occupations by average income in that occupation in 1950
• Educational attainment (not available for 1900–1930)
• Home ownership (not available for 1900–1930)

Since the labor-force participation and earnings patterns of males and females have historically been quite distinct, the index measures the immigrant-native differences in these factors separately by gender.

Cultural assimilation is the extent to which immigrants, or groups of immigrants, adopt customs and practices indistinguishable in aggregate from those of the native-born. Factors considered in the measurement of cultural assimilation include intermarriage and the ability to speak English, which have been the focus of many previous efforts to track immigrant assimilation in the United States. Cultural assimilation also incorporates information on marital status and childbearing. It is important to note that cultural assimilation is not a measure of a group’s conformity with any preconceived ideal. Changes in the customs and practices of the native-born can promote cultural assimilation just as easily as changes among the foreign-born.

Some of the most spirited charges in immigration policy debates concern the cultural aspects of immigrants’ integration into American society. While some aspects of this debate, such as the value of traditional American culture, are relatively abstract, other aspects are very concrete. State and local governments, for example, often face cost burdens associated with providing services—most notably, public education—to non-English-speaking immigrant groups.[13] Incorporating childbearing patterns into the index allows it to measure the potential impact of immigration on public schools in the near term, and on broader fiscal issues in the long term. Marital patterns, including the decision to marry a native-born spouse, or the decision to reside in the United States without one’s spouse, provide clues as to immigrants’ long-term intentions, which are critical to understanding the long-term fiscal impact of immigration.

The following factors are used to measure cultural assimilation:

• Ability to speak English
• Intermarriage (whether an individual’s spouse is native-born)
• Number of children
• Marital status

Civic assimilation is a measure of immigrants’ formal participation in American society, primarily through naturalization. Since native-born residents of the United States are citizens by default, civic assimilation increases as the proportion of immigrants who are naturalized citizens increases. The index of civic assimilation also incorporates information on past or present military service, except in the years from 1900 to 1930. Since military service is more common among males than females, the index measures the immigrant-native difference separately by gender. Both naturalization and military service are signals of a strong commitment to the United States—though the power of these signals is directly influenced by government policy. The government sets standards for naturalization and, to some extent, determines the benefits of naturalization, by setting differential policies for citizens and noncitizens; military recruitment needs determine the number of opportunities for service in the armed forces. Changes in civic assimilation could, in theory, reflect either changes in immigrant civic attitudes or changes—perhaps even anticipated changes—in policy. It is important to note that the Census Bureau collects no information on immigrants’ legal status, which means that this study cannot use legal status as a factor in the computation of civic assimilation.

To some extent, civic assimilation is an even stronger indicator of immigrants’ intentions than cultural assimilation. The choice to become a naturalized citizen, or to serve in the United States military, shows a tangible dedication to this country. Civic assimilation may thus forecast the long-run impact of immigration, both in a concrete fiscal sense and in a more abstract cultural sense.

The information in this report will not settle larger debates over immigration policy. Assimilation may not be necessary for immigrants to make net positive contributions to society. Assimilation may even be undesirable under certain circumstances. For example, immigration may have the most positive net impact on economic growth if immigrants are economically distinct from natives. Immigrants may choose to naturalize because they fear a change in immigration policy rather than because they wish to make a commitment to the United States. Detailed information on immigrant assimilation will help those wishing to make reasoned arguments in the immigration policy debate, but it will not resolve the controversies in and of itself.

The remainder of this report is structured as follows. Chapter 2 reports basic results for 2006. Chapter 3 places these results in context by reporting additional index calculations for the period between 1900 and 2005. Whereas the assimilation index itself provides only a snapshot of immigrants’ status in the host society, analysis of data over time can actually illuminate the assimilation process itself and changes in that process over time. Chapter 4 augments the analysis by studying immigrants belonging to “Generation 1.5,” those individuals born abroad but brought by their parents to the United States before they commenced their formal education. Chapter 5 presents an in-depth analysis of three immigrant groups: contemporary Mexican immigrants; contemporary Vietnamese immigrants; and the Italian immigrants of the early twentieth century. Chapter 6 summarizes the main conclusions of the study. The final chapter is a detailed methodological appendix.


2. Assimilation in 2006

Taken out of context, it is impossible to pass judgment on whether a single number is high or low. With this fundamental caution in mind, this chapter briefly presents information on the state of assimilation in 2006, the most recent year for which relevant data are available. In addition to the overall index values for all foreign-born working-age adults in the United States, this chapter provides a few simple breakdowns by immigrants’ country of origin and metropolitan area of residence. More complete tabulations along these lines are available in the Appendix.

The assimilation index ranges from zero to 100. An index close to the minimum value of zero implies that one who relies on only the information used to compute the index can almost perfectly distinguish the foreign-born from the native-born. An index close to the maximum value of 100 indicates that attributions of foreign birth are no more accurate than random guessing.

In 2006, the composite assimilation index, which reflects an attempt to predict individuals’ nativity on the basis of economic, cultural, and civic indicators, took on a value of 28. The algorithm for distinguishing the foreign-born from the native-born is not perfect (that is, the assimilation index is not zero), but it performs much better than random guessing. It correctly identifies foreign-born individuals as immigrants, in a sample consisting of equal numbers of foreign- and native-born adults, in nearly seven-eighths of all cases.

The algorithm used to infer whether an individual was born in the United States or abroad takes advantage of the following patterns in the American Community Survey for 2006:

Foreign-born residents of the United States are:
  • Perfectly distinguishable from natives when they are not citizens of the United States.
  • Much more likely to be married to another foreign-born individual.
  • Much less likely to be able to speak English.
  • Less likely to own their residence.
  • More likely to have larger numbers of children living with them.
  • Overrepresented at the low and high ends of the educational distribution; and underrepresented in the group of individuals with no more than a high school diploma, or with some college education but no degree.
  • Less likely to be unemployed or absent from the labor force.
  • Less likely to be veterans.
  • More likely to be working in historically higher-paying occupations but earning less than natives working in those occupations.

Among these patterns, the first three are by far the strongest determinants of the assimilation index.

Figure 2 shows the relative magnitude of the composite assimilation index, as well as the three component indexes, which focus on cultural, civic, or economic indicators, respectively. Immigrants display the greatest degree of assimilation, according to these measures, along economic lines.[14] The 2006 index of economic assimilation is 87. Using only information on labor-force participation, income, occupation, home ownership, and educational attainment, the best model for distinguishing the native-born from the foreign-born performs only slightly better than random guessing—making the correct guess about 56% of the time instead of 50%.

The distinction between immigrants and natives is stronger along cultural dimensions—marriage and childbearing patterns, along with English-speaking ability. The 2006 index of cultural assimilation is 62, indicating that the statistical model produces correct guesses just over two-thirds of the time.[16] Finally, the greatest degree of distinction is along civic lines—citizenship and military service. The 2006 civic assimilation index of 41 indicates that these two indicators by themselves can correctly predict nativity in nearly 80% of all cases. From another perspective, adding all the cultural and economic indicators to the civic indicators moves the index a relatively short distance, from 41 to 28.

The composite index is not a simple average of the three component indexes. Each index is a measure of the power of a statistical algorithm to distinguish the native-born from the foreign-born on the basis of a set of indicators. When the algorithm can distinguish more powerfully, the index is lower—that is, it is easier to tell the difference between the two groups. The algorithm used to compute the composite index combines the three distinct sets of information that produce the individual component indexes. By using the widest range of information, the composite index has a natural advantage in distinguishing the native-born from the foreign-born. This natural advantage implies that the composite index will almost always be lower than any of the three components for a given group of immigrants.

Both composite and component assimilation indexes can be computed for subgroups of the immigrant population. Figure 3 shows the degree of assimilation of a set of ten large country-of-origin groups in 2006.16 Among these large groups, the assimilation index varies from a low of 13, for those born in Mexico, to a high of 53, for those born in Canada. The assimilation index is below the overall average of 28 for immigrants from Mexico, El Salvador, China, and India. Immigrants born in Canada, Cuba, the Dominican Republic, Korea, the Philippines, and Vietnam have assimilation-index values higher than the national average.

Figures 4, 5, and 6 plot the component assimilation indexes for the same ten large country-of-origin groups. Figure 4, covering economic assimilation, shows that four of these ten groups are economically indistinguishable from natives, and two more are close to indistinguishable. Immigrants from Mexico are the least economically assimilated of any group, with those from El Salvador a close second. Individuals born in the Dominican Republic and China also display economic assimilation levels at or below the national average.

Figure 5 shows a country-of-origin group, Canadians, that can claim to be culturally indistinguishable from native-born Americans. Immigrants born in the Philippines and the Dominican Republic also show relatively high levels of cultural assimilation. At the other end of the spectrum, immigrants born in China and India show the greatest degree of cultural distinction from the native-born. It is interesting to note that both these groups show average or above-average levels of economic assimilation, a first clue that cultural assimilation is not a prerequisite for economic assimilation. The least economically assimilated large group, the Mexican-born, posts cultural assimilation levels nearly identical to those of Vietnamese immigrants, who are nearly indistinguishable from the native-born along economic lines.

Figure 6 rounds out the picture by displaying civic assimilation levels for the same set of countries of origin. Unsurprisingly, given illegal immigrants’ ineligibility for citizenship or military service, Mexican and Salvadoran




immigrants show the lowest degree of civic assimilation. More surprisingly, Canadians, despite their full economic and cultural integration with the native-born population, display only a modest degree of civic assimilation. Given the common border of Canada and the United States, Canadian immigrants may view their stay in this country as temporary and the naturalization process as unnecessary.

The country-of-origin groups with the highest degrees of civic assimilation have a common legacy of American military intervention at some point in the twentieth century. Foremost among them are immigrants born in Vietnam, who are more assimilated along civic dimensions than any other large group in 2006. This achievement is particularly noteworthy given Vietnamese immigrants’ unremarkable degree of cultural assimilation, as well as their level of economic assimilation, which is slightly below that of natives of Canada, Cuba, Korea, and the Philippines.

In addition to computing degrees of assimilation of individual country-of-origin groups, the index can evaluate all immigrants residing in a particular metropolitan area. A complete set of index numbers for areas with significant immigrant populations can be found in the Appendix. Figure 7 shows the index values for the ten largest immigrant destinations in 2006.[17] To a large extent, variation across metropolitan areas can be explained by variation in the country-of-origin groups most strongly represented in the population. Houston, with its proximity to Mexico, has the lowest assimilation-index value in this set of metro areas. Los Angeles, which has a very large Mexican population along with considerable numbers of Asian immigrants, is above Houston but below most other metropolitan areas. The polyethnic New York City area, which attracts a number of European immigrants in addition to people from the developing world, has the second-highest index value among the metropolitan areas shown here. Washington, D.C., also claims a relatively high index value. Miami, with its large concentration of immigrants from Cuba and other Caribbean nations, posts an index value slightly higher than the national average. Somewhat surprisingly, San Diego, in spite of its close proximity to the Mexican border, registers as the destination with the highest assimilation index among those listed here.

To this point, reported index values have provided a simple snapshot of a dynamic process. Assimilation does not occur instantaneously but rather evolves as immigrants learn more about the host society and take steps, both formal and informal, toward more complete participation in it. Chapter 4, which expands the study of the assimilation index backward through time, will provide an opportunity to observe this process. Figure 8 presents a different type of opportunity by comparing the 2006 assimilation-index values of immigrants who report having arrived in the United States at varying points in time.

There are several reasons that immigrants who arrived at varying points in time might exhibit varying degrees of assimilation in 2006. As stated above, one reason is that the assimilation process takes time. A second reason is selective return migration. Immigrants who experience difficulty in their transition to the host society, and therefore look poorly assimilated when here, may be more likely to return to their origin country, or move on to a different host country.[18] The set of immigrants who remain in the United States for an extended period of time will then appear more assimilated, even if their rate of assimilation has been quite modest. Finally, changes in immigration policy or world economic, social, and political conditions may change the composition of the immigrant population over time. Immigrants who arrived prior to 1965, for example, faced a different immigration policy from ones confronting more recent arrivals, and may differ for that reason. The trends in Figure 8 may reflect any of these explanations. Longitudinal analysis in the next chapter will be able to rule out the third explanation but will not distinguish between the first two.

Consistent with both the view that immigrants assimilate over time and that immigrants who fare poorly are more likely to depart, there are several clear positive trends in Figure 8. In 2006, immigrants who arrived in the United States within the previous year or two are easily distinguished from the native-born, primarily because they are very unlikely to be citizens. The composite and civic assimilation indexes for this group are very close to zero. By comparison, immigrants who arrived ten years earlier, in the mid-1990s, post overall assimilation-index values of around 20 and civic assimilation-index values closer to 30. Immigrants who arrived in the mid-1980s had by 2006 attained a composite-index value of 30 or higher. The most assimilated immigrants shown here are those who arrived in the mid-to-late 1960s. This group posts composite-index values in the 60–70 range.

There are interesting contrasts among the component assimilation indexes in Figure 8. Civic assimilation, unsurprisingly, begins close to zero but increases steadily, reaching values near 80 among immigrants who arrived a generation ago. Economic assimilation also shows an unmistakable upward trend, beginning in the mid-70s for recent arrivals and nearing the maximum value of 100. Cultural assimilation shows a comparatively weak trend among more recent immigrants; as of 2006, immigrants who arrived in the mid-1980s posted assimilation-index values only a few points higher than the most recent arrivals. A more recognizable upward trend appears among immigrants arriving prior to the mid-1980s. Some portion of this trend may be attributable to the experience of immigrants who arrived as youths in the 1960s or 1970s, learned English in the public schools, and married here in the United States rather than abroad. Chapter 5 will consider this type of first-generation immigrant in greater detail. While caveats apply to this analysis, as it is based on cross-sectional rather than truly longitudinal information, this evidence points once again to the conclusion that the process of cultural assimilation is not a necessary precursor of either economic or civic assimilation.


3. Assimilation in Historical Context


To study assimilation as a process and to determine whether that process has changed over time in the United States, it is necessary to move beyond a single year’s snapshot and examine longitudinal information on the assimilation of immigrants in the United States. Figure 9 begins this study by presenting time-series information on the progression of the assimilation index over the past quarter-century, using data drawn from the Census enumerations of 1980 and 1990, as well as the annual American Community Survey conducted since 2000.

As shown in Figure 1, the period between 1980 and 2006 experienced tremendous growth in the immigrant population of the United States. Driven primarily by increased immigration from Latin America and Asia, the number of foreign-born residents of the United States nearly tripled in this time period. Figure 9 shows that this growth has had very little impact on the assimilation index. There has been some degree of decline in the composite index and each of its components since 1980; but in most cases, the decline is confined to the 1980s. Between 1990 and 2006, a period when the immigrant population doubled, the composite index and each of its components remained effectively unchanged. If there is any evidence of a trend in recent years, it is toward increased assimilation. The composite index shows a small uptick just after 2000; the civic assimilation index reached its low point in 1990; both cultural and economic assimilation are higher in 2006 than they were just four years earlier.[19] Thus, while it is true that each assimilation index is lower than it was in 1980, the lack of any noticeable trend in the past 16 years—and, in fact, the evidence of slight increases in assimilation in spite of continued growth in the immigrant population—is noteworthy.

The relative stability of the assimilation index since 1990 is even more striking when compared with the trend in the previous great wave of immigration to the United States, in the early twentieth century. Figure 10 provides some background information on this earlier wave of immigration. Between 1870 and 1920, the number of foreign-born residents of the United States more than doubled, in large part as the result of the arrival of immigrants from Southern and Eastern Europe. Because the Census did not collect certain critical pieces of information—most notably, whether the immigrants in question could speak English—the earliest possible date for computing the assimilation index is 1900. Moreover, much of the data used to compute the assimilation index between 1980 and 2006 were not collected by the Census Bureau between 1900 and 1930. The following historical analysis is based on a consistently computed alternative version of the assimilation index, which considers the exact same set of factors for all the years between 1900 and 2006.

Figure 11 shows that between 1900 and 1920, a period when the immigrant population of the United States grew by roughly 40%, the assimilation index declined substantially, from an initial value of 55 to 42. After 1920, as more severe restrictions were placed on immigration, the index rebounded somewhat, to a level surprisingly similar to that observed in 1980, the beginning of the modern era of immigration. By this index measure, which is based for purposes of comparison on only the information available in early Census enumerations, the drop in the assimilation index between 1980 and 1990 was more precipitous than that depicted in Figure 9. The period between 1990 and 2006 continues to be marked by the lack of a net trend in assimilation.

In this century-long perspective, two noteworthy aspects of the current assimilation index emerge. First, the index since 1990 has taken on a value well below the lowest point observed in the previous wave of immigration to the United States, which occurred in 1920. Bear in mind that even in 1920, the majority of foreign-born residents of the United States were natives of Northern or Western European nations, or of Canada. By 1990, these countries of origin represented a much smaller proportion of all immigrants. Second, the rapid growth of the immigrant population since 1990 has not occasioned a decline in assimilation comparable in scale with that witnessed between 1900 and 1920, when the immigrant population grew at a much slower rate.

If the duration of immigrants’ stays in the United States were the only determinant of their degree of assimilation, we would expect periods of more rapid growth in the immigrant population to be periods of declining assimilation-index values because the proportion of that population that was newly arrived would be relatively large. The assimilation index is clearly influenced by other factors, however. Federal policy influences rates of naturalization and induction into the military; moreover, certain immigrant groups, notably those from English-speaking nations, arrive in the United States with a head start. The impact of new immigrant arrivals on the assimilation index, then, can be either diminished or augmented by changes in policy or changes in the composition of the flow of immigrants.

Figure 12 shows how these factors can help explain both the low level of the assimilation index observed since 1990 and the stability of the index during this time period compared with earlier episodes of rapid growth in the immigrant population. It plots the assimilation-index value for immigrants who arrived in the United States within the past five years, for Census enumerations in 1900, 1910, 1920, 1980, 1990, and 2000, and for the American Community Survey for 2006. The shift in the composition of the immigrant population between 1900 and 1920, away from Northern and Western Europe and toward Southern and Eastern Europe, is evident in the first three points on the chart. In 1900, newly arrived immigrants posted an assimilation index of over 20; by 1920, this value had fallen by more than two-thirds, to 7. In more recent years, the assimilation of newly arrived immigrants has been consistently low, ranging from around 8 in 1980 to just over 2 in 2000, but has not displayed the strong downward trend evident in the first two decades of the twentieth century. There has been, in fact, an uptick in the assimilation of newly arrived immigrants since 2000.

A more complete picture of the change in the assimilation process that took place between 1900 and 1920 appears in Figure 13. This figure mirrors Figure 8 above, plotting the assimilation index for immigrants according to the number of years since their arrival. In all years, immigrants with more experience of the United States tend to be more assimilated. Note, however, that the assimilation “hill” representing the year 1920 is at almost every point lower than the hills representing 1910 and 1900. The hill representing 1910 is likewise lower than the 1900 hill for the first 20 years or so. Thus, the tendency of newly arrived immigrants to be less assimilated in 1920 than they were in 1900 or 1910 applies at other points in the assimilation process as well. Immigrants arriving in 1900 were considerably less assimilated in 1920 than the immigrants of 1880 were in 1900. Between 1900 and 1920, growth in the immigrant population was accompanied by a slowdown in the assimilation process.

Figure 13 also includes assimilation hills for 2000 and 2006 (data from the 1980 and 1990 Census enumerations are not sufficiently rich to permit similar plots for those years). In contrast to the earlier period, when each decade’s hill lay below the one immediately preceding it, there is a substantial degree of overlap between the 2000 and 2006 hills at virtually all points. These two hills are also lower than those of the early twentieth century, which explains why contemporary composite assimilation is lower than it was in that earlier period.

These “assimilation hills” show that at any given point in time, immigrants who have been in the United States for a longer period of time are more assimilated. One might also conclude from these graphs that the assimilation index tends to rise for individual cohorts as they spend more time in the United States. There is an alternative explanation, however, which graphs like Figure 13 and its earlier counterparts cannot rule out: that immigrants who entered long ago have always been more assimilated than those who arrived recently. There are a few clues in Figure 13 that this is not the case. The newly arrived immigrants of 2000, for example, are the immigrants who in 2006 had arrived six years earlier. It is difficult, however, to use a graph like Figure 13 to track one cohort’s progress. Figures 14 through 18 make the job easier. Rather than compare the experience of many different cohorts at a single point in time, these graphs follow the progress of individual cohorts across multiple points in time.

Figure 14 presents true longitudinal information on the progress of immigrant cohorts between 1900 and 1930, focusing on three groups: those arriving between 1895 and 1900, between 1905 and 1910, and between 1915 and 1920. Consistent with Figure 12, each cohort begins at a lower level of assimilation than the one immediately preceding it. Moreover, the cohorts exhibit differing rates of progress over their first full decade in the United States. The earliest-arriving group posts a 20-point increase in the assimilation index between 1900 and 1910. This gain is followed by much weaker progress in the second decade. The second cohort shows a much smaller increase over its first decade. Between 1920 and 1930, assimilation accelerates for all three groups. The overall decline in assimilation between 1900 and 1920 reflects both the decline in initial position across cohorts and the tepid progress of all cohorts in the period 1910 to 1920.

Figure 15 presents a comparable picture for the period 1980 to 2006.[20] Consistent with the information in Figure 12, there is some evidence of a slight decline in the assimilation of newly arrived immigrants over this time period. Tracked over time, however, each cohort appears to show little slowdown in the rate of assimilation; each has either posted, or appears on track to post, an increase of 15 to 18 points over



its first decade, followed by gains at the same rate or faster in the second decade. The newly arrived immigrants of 1975–80 appear much less assimilated than their counterparts arriving in 1895–1900. The more rapid progress of the more recent cohort implies that this group, as of 2006, appears only slightly less assimilated than the earlier cohort did in 1930.

Although the immigrants of the late twentieth century were less assimilated at the time of their arrival than their counterparts in the opening decades of the century, their subsequent assimilation was more rapid. To what can we attribute this difference? Figures 16 through 18 help answer this question by tracking the economic, civic, and cultural assimilation of individual cohorts over time. Figure 16 shows that cohorts of modern immigrants have exhibited steady economic assimilation over time, posting strong gains in the economic assimilation index in the first decade in the United States and continued progress thereafter. As mentioned above, some portion of this progress may reflect the exit of unsuccessful immigrants rather than improvements in the status of remaining immigrants. Note that the rate of progress shown by these cohorts, between 7 and 10 points over the first decade, is greater than the difference in assimilation between cohorts, as shown in Figure 8. This contrast is explained by another pattern visible in Figure 16: the cohorts arriving between 1995 and 2005 exhibit lower initial levels of economic assimilation than the cohort arriving between 1985 and 1990.

Figure 17 shows that civic assimilation has also increased steadily for recent cohorts of immigrants, posting gains in the 20- to 30-point range over the first decade, with continued progress thereafter. This degree of progress is generally consistent with the across-cohort comparison in Figure 8. The steady assimilation of immigrants arriving after 1975 can thus be traced both to improved economic fortunes among those immigrants who remain in the country and to steady increases in the fraction of immigrants who are naturalized citizens and who have served in the U.S. military.

Figure 18 presents something of a contrast with the earlier plots but one consistent with the basic across-cohort evidence in Figure 8. The immigrants arriving in the late 1970s, as well as those arriving in the late 1980s, show very little increase in cultural assimilation over their first full decade in the United States. In both cases, this decade-long period of dormancy is followed by significant increases in the rate of cultural assimilation. More recent cohorts of immigrants appear to have bypassed the dormant period, posting more immediate increases in cultural assimilation. The delayed onset of cultural assimilation may reflect a tendency of immigrants to intermarry later in life (perhaps when entering into second or higher-order marriages), or the ascendance of younger members of the cohort who were brought to the United States as children.

Overall, then, the study of historical data is of great value in understanding the assimilation of immigrants to the United States in the twenty-first century. The assimilation index is low overall, and has been at a steady low level since 1990. This 16-year period is unique, however, in that it coupled a rapid increase in the immigrant population with virtually no change in the composite assimilation index or its components. Over the past few years, in fact, there has been some evidence of an upward trend in assimilation. Rapid growth of the immigrant population, which would tend to depress the assimilation index on its own, was offset by stronger upward trends in assimilation for immigrants remaining in the United States. These strong upward trends are most obvious along economic and civic dimensions. Cultural assimilation shows less evidence of increasing strongly as immigrants spend more time in this country, except among cohorts arriving within the past decade.


4. Case Studies: Mexico, Vietnam, and Italy


By a substantial margin, Mexico was the largest source of immigrants to the United States in 2006. Between 1980 and 2006, the number of Mexican-born residents of the United States more than sextupled, to nearly 11 million, representing an annual growth rate of over 6%, which was more than five times the growth rate of the U.S. population over the same time period. This growth rate accelerated after 1990. A large proportion of these immigrants live and work in the United States illegally. Finally, as shown in the basic summary in Chapter 2, Mexican immigrants attain the lowest assimilation-index value among large immigrant groups, both in the composite index and in the component indexes of economic and civic assimilation.

For these reasons, contemporary immigration policy debates center on the problem of immigration from Mexico. This chapter narrows the analysis of immigrant assimilation presented in previous chapters to focus on the experiences of Mexican immigrants. For purposes of comparison and contrast, two other country-of-origin groups are presented as case studies here. Vietnamese immigrants provide an interesting contrast. As shown in Chapter 2, this country-of-origin group shows some evidence of successful assimilation, particularly in the civic dimension. If the goal of immigration policy is to encourage newcomers to follow the path toward citizenship, the case of Vietnamese immigrants may represent a modern ideal. The population of immigrants from Vietnam has also grown at rates very close to those that the Mexican-born population exhibited between 1980 and 2006, although the growth of the Vietnamese immigrant population was concentrated in the early, rather than the late, part of the period.

The second comparison group is Italian immigrants arriving in the United States between 1895 and 1920. Like Mexicans today, Italian immigrants formed the largest single country-of-origin group in the early twentieth century.[21] Immigration from Italy and other poor nations in Southern and Eastern Europe inspired much of the policy debate that led up to the imposition of national origin quotas in the 1920s.

The strong contrast between Mexican and Vietnamese immigrants can be seen in Figure 19, which plots, in terms of the composite assimilation index, the progress made by four cohorts: those arriving in the late 1970s, late 1980s, late 1990s, and early 2000s. Newly arrived immigrants from both countries post very low, and very similar, index values in the Census enumerations of 1980 and 1990. These cohorts’ progress over the subsequent decade is far from uniform. The Vietnamese immigrants of the late 1970s attained a composite-index value of nearly 40 by 1990. Mexican immigrants of the same time period scarcely reached a value of 10 that same year, despite having started at a slightly higher level. An even stronger contrast can be seen among the arrivals of the late 1980s. By 2000, the Vietnamese immigrants in this cohort had once again neared an index value of 40, while their Mexican counterparts had posted very little improvement.

Cohorts arriving after 1995 have been more distinct upon arrival, with Vietnamese immigrants tending to appear more assimilated at the entry point. The pattern for Vietnamese immigrants of swifter assimilation continues, however.

It bears repeating at this point that the changes in the assimilation index viewed here could, in theory, reflect either of two mechanisms: Vietnamese immigrants may truly experience faster acclimation to American society over time; or they may be more likely to exit the country in the event that they assimilate poorly.[22]

How do these two polar cases compare with the experience of Italian immigrants of the early twentieth century? Figure 20 shows that Italians serve as something of an intermediate case. Italian immigrants of 1895–1900, and of 1905–10, are very poorly assimilated upon arrival, with index values quite similar to those of newly arrived Mexicans and Vietnamese in 1980 and 1990. Their progress in the subsequent decade is faster than that of recent Mexican immigrants but slower than that of recent Vietnamese, with index values rising to the upper teens for both cohorts. Italian immigrants arriving between 1916 and 1920, a period when the overall flow of immigrants to the United States had slackened considerably, show signs of rapid assimilation between 1920 and 1930, though still not as rapid as that exhibited by recent cohorts of Vietnamese immigrants.

If the long-run image of early-twentieth-century Italian immigrants is that they were successful in assimilating into American society, then a comparison of their early assimilation trajectory with the two recent cohorts now under analysis leads to some quick conclusions. Vietnamese immigrants, taken as a whole, are well on track to be considered successful. Mexican immigrants, by contrast, display much more worrisome patterns.

If these two groups are indeed on different trajectories, is there any policy solution that might encourage stronger assimilation on the part of Mexicans? Put differently, if we could change one aspect of Mexican immigrants so as to make their experience more like that of the Vietnamese, what might that change be?

To think about these hypothetical questions, it is useful to examine the component assimilation indexes for the cohorts studied in Figure 19. Figure 21 begins the process by plotting the economic assimilation of members of the two groups, by arrival cohort, between 1980 and 2006. Here, a strong contrast between groups appears. Vietnamese immigrants, particularly those in the first arrival cohort, display a much greater degree of economic assimilation upon arrival. Economic assimilation for newly arrived Mexicans in 1980 is around 50, whereas for Vietnamese immigrants it is over 85. Not only do immigrants born in Vietnam begin at a higher economic level; they show stronger signs of economic assimilation over time. The sole exception to this pattern is among those arriving in the United States between 2001 and 2005; in this group, Vietnamese immigrants enjoy a clear starting advantage but appear to regress between 2005 and 2006, whereas there are signs of real progress among Mexican immigrants. This intriguing contrast will merit further observation as more data become available in future years.

Strong contrasts between groups appear once again in Figure 22, which examines trends in the civic assimilation index by country of origin and arrival cohort between 1980 and 2006. Immigrants from both nations start at low levels of assimilation in each cohort. Vietnamese immigrants arriving in the late 1970s, late 1980s, and late 1990s make considerable progress over their first full decade in the United States. Mexican-born immigrants make very little progress. This contrast does appear to extend to the cohorts arriving after 2000.

Why do Vietnamese immigrants start at a higher economic level, and make more rapid progress along both economic and civic dimensions? While a complete discussion of the differences could consume an entire monograph, several easy explanations bear brief discussion. Vietnam, at least in the early part of the time period under study, was a Communist country lacking normal diplomatic and trade relations with the United States. The set of individuals choosing to flee a Communist nation to settle in a nation with a free-market economy likely included a high proportion of entrepreneurs or skilled workers seeking better compensation. The costs of exiting Vietnam and making the trip to the United States were substantial, and the costs of returning to Vietnam after settling here would also have been great. Vietnamese immigrants had relatively strong incentives to achieve full membership in American society. As political refugees, many also benefited from favorable naturalization rules.

For Mexicans, the costs of moving to the United States from Mexico are not so substantial. While the United States is undoubtedly an attractive location for highly skilled and entrepreneurial Mexican-born workers, it also offers wages and living standards much higher than lower-skilled Mexican workers could expect in their own country. Those Mexicans who enter the country illegally stand no chance of progress along the lines of civic assimilation, and they surely face considerable barriers to significant economic advancement. Even if provided the opportunity to progress toward citizenship, Mexican immigrants’ incentives to do so may be muted should they intend to return to their home country after a brief stay in the United States.

Do the contrasts in assimilation between Mexican and Vietnamese immigrants extend to the cultural dimension? Figure 23 shows that the answer, perhaps surprisingly, is no. Among cohorts arriving in the late 1970s or late 1980s, an immediate upward trend in cultural assimilation appears only for Mexican immigrants. A possible explanation for this pattern concerns marriage patterns. Immigrants who are unmarried upon arrival, but marry a foreign-born spouse sometime over the next ten to 15 years, will register a decline in cultural assimilation unless it is offset by a second factor, such as improvement in English-speaking skills. Mexican immigrants may be less likely to marry a foreign-born spouse simply because there exists a substantial population of native-born individuals of Mexican descent. A second possible explanation is language: Vietnamese is a tonal, Austro-Asiatic language; the differences between Vietnamese and English are much more profound than the differences between Spanish and English.

Note that for both cohorts and both groups, progress toward cultural assimilation appears after the first full decade, driven possibly by the aging of individuals brought to the United States as children.

As was found in previous analyses of cultural assimilation, patterns look very different for immigrants arriving after 1995. For both Mexican and Vietnamese immigrants of this vintage, there are signs of immediate progress toward cultural assimilation. Vietnamese immigrants in the 1995–2000 cohort begin at a lower level but make more rapid progress than Mexicans; Vietnamese immigrants in the 2001–05 cohort begin at a higher level but make less rapid progress than Mexicans in this cohort.

Why have the most recent cohorts experienced more immediate gains in cultural assimilation? Changes in marriage patterns may explain part of the phenomenon. By the late 1990s, both groups would have had access to a larger pool of potential spouses in the same ethnic group who were born in the United States. Attitudes toward intermarriage may have also changed within these groups, or among potential spouses for members of these groups. This promising sign of more rapid progress in the most recent cohorts of immigrants merits further study.

What have we learned from this analysis of individual groups? The greatest marks of distinction between immigrant groups that have assimilated rapidly and slowly, taking these groups as a guide, are along the economic and civic dimensions. As first intimated in Chapter 3, cultural assimilation does not appear to be a prerequisite for assimilation along the other two dimensions. This pattern implies that policies restricting bilingual education, or requiring that government business be conducted in English, will have little impact on economic or civic assimilation. Indeed, erecting linguistic barriers to civic participation might actually retard assimilation along noncultural lines. Some observers may believe that policies promoting cultural homogenization are desirable. What should be clear, however, is that such policies do not appear to promote civic or economic assimilation.


5. The Next Generation


Assimilation can be thought of as a process whereby foreign-born individuals come to resemble the native-born along cultural, civic, and economic lines. Assimilation can also be thought of as an intergenerational process, leading the children of immigrants to bear a stronger resemblance to the native-born population than their parents ever did. An evaluation of the assimilation process, then, should consider the progress made by immigrants’ children as well as by first-generation immigrants themselves.

In principle, the same method used to evaluate the assimilation of first-generation immigrants could be applied to later-generation immigrants. The goal would be to measure the difficulty of distinguishing native-born citizens with foreign-born parents from those with native-born parents. In practice, this goal is difficult to attain using Census and American Community Survey data, since the Census has not collected information on parents’ birthplace since the 1970 enumeration. Previous studies of second-generation immigrants have adopted two basic strategies for overcoming this data deficiency. The first is to switch to a different data source, the Current Population Survey (CPS), which has collected information on parental birthplace since the mid-1990s.[23] The second is to analyze Generation 1.5, the set of individuals born abroad but raised since childhood in the United States. This second strategy has the advantage that it can be pursued consistently from 1900 to 2006, while using the same data source as the preceding analysis of first-generation adults.

This section presents an alternative assimilation index for foreign-born adolescents and young adults who were brought to the United States as children. The subjects here are between the ages of 12 and 24 and arrived in the United States when they were at most five years old. Thus each individual analyzed here received formal education almost exclusively, if not exclusively, in this country. Individuals born abroad to American parents are excluded from the analysis. As in the standard assimilation index, the goal of this analysis is to determine how well a statistical model can distinguish the native-born from the foreign-born in a sample constructed to contain equal numbers of each.

The decision to use a different set of factors to compute this alternative index reflects the fact that many factors considered in the study of adults, such as earnings and military service, are not appropriate for a study of adolescents and young adults. In this analysis, the following factors enter into the statistical algorithm used to predict nativity:

• Residence in group quarters. Group quarters are defined by the Census Bureau as any institutional dwelling, or a dwelling housing a large number (usually ten or more) of individuals unrelated to the household head. The Census distinguishes between those individuals residing in institutions and those residing in college dormitories or military housing. The primary purpose of including this variable is to discern whether there are differences in incarceration rates between native- and foreign-born adolescents and young adults. Group-quarters information is not available in the American Community Survey covering the years from 2000 to 2005.
• Ability to speak English
• School attendance
• Marital status (whether ever married)
• Childbearing (whether the individual is a parent)
• Labor-force participation
• Residence with own parents

The last five factors (school attendance, marital status, childbearing, labor-force participation, and residence with own parents) are permitted to influence the algorithm’s computations in ways that vary by age. At age 15, for example, it is quite exceptional not to be enrolled in school. Among 24-year-olds, however, it is not at all uncommon. Similarly, the likelihood of being a parent, living with one’s own parents, participating in the labor force, and having been married change as an individual ages from 12 to 24. The algorithm will use any differences in the patterns exhibited by native- and foreign-born adolescents to help distinguish between them.

Some calculations of the assimilation index for immigrants’ offspring add citizenship as a factor; others do not. Rather than divide the distinguishing characteristics into economic, cultural, and civic subgroups, this analysis will effectively partition the factors into “naturalization,” which basically mimics civic assimilation, and “all other,” denoting a combination of economic and cultural factors. It should be noted that citizenship cannot be used as a distinguishing characteristic in 1900 and 1910 because the Census questionnaire did not collect information on the citizenship of individuals under the age of 21 in those years.

In 2006, the algorithm used to distinguish between adolescents and young adults born in this country or abroad takes advantage of the following patterns in the American Community Survey:

• Adolescents and young adults born abroad, but brought to the United States by age five, are:

  • Perfectly distinguishable from natives when they are not citizens of the United States.
  • Much less likely to speak English.
  • Less likely to reside in group quarters.
  • More likely to have been married at any particular age.
  • Less likely to be enrolled in school when between the ages of 17 and 22.
  • More likely to be enrolled in school at the ages of 23 or 24.
  • Less likely to be a parent.
  • More likely to live with their own parents between the ages of 18 and 24.
  • Less likely to participate in the labor force at ages 16 through 19, and at ages 22 through 24.

The distinctions between young immigrants and native-born adults are troubling in some respects but not others. The higher tendency to drop out of school is a frequently analyzed concern regarding children of immigrants from Mexico and its neighbors. The lack of English ability in a group of young immigrants who have spent a minimum of seven years in the United States also warrants concern. The lower rates of teen parenthood and higher rates of school enrollment at ages typically associated with postgraduate education are encouraging, but this latter pattern in particular may reflect the experiences of a very different subgroup of foreign-born but American-raised young adults.

Perhaps the most important generalization to be made about the differences between native- and foreign-born adolescents and young adults is that they are relatively small. This conclusion is readily seen in Figure 24, which tracks the assimilation of Generation 1.5 using indexes that include and exclude citizenship as a distinguishing characteristic for the years 1900 through 2006. For this 107-year time period, the assimilation index excluding citizenship is consistently high, never falling below a value of 90. Without incorporating information on citizenship, it remains difficult to distinguish individuals raised in the United States but born in different countries. When citizenship is used as a distinguishing variable, it becomes much easier to differentiate the two groups. Assimilation-index values including citizenship information range from the mid-40s in the early part of the twentieth century to a low of 18 in 1980, and have trended back upward into the 40s in recent years. While the assimilation index shows signs of increasing in recent years both among adult immigrants and their foreign-born children, the trend is more pronounced in Generation 1.5. This increase has been driven primarily by increased naturalization rates among individuals born abroad but raised in the United States.

Chapter 3 presented evidence that immigrants arriving between 1975 and 1990 showed few signs of cultural assimilation over their first decade or more of residence in the