Immigration has been the key to this demographic evolution. It has contributed to the rapid growth of the Asian and Hispanic populations since the 1960s. In 1997, 38 percent of the Hispanic population and 61 percent of the Asian population were foreign-born, compared with eight percent of the white population, six percent of the African American population, and six percent of the Native American population. The increased immigration of Asians and Hispanics over the past several decades is largely the result of changes in immigration policy. In particular, the 1965 Immigration Act ended the system of national origin quotas that had previously restricted immigration from non-European countries. The Immigration Reform and Control Act of 1986 also contributed to the increase in the documented Asian and Hispanic populations by legalizing a large number of immigrants.

While immigration of Asians and Hispanics has increased, population growth has slowed dramatically for the United States as a whole, largely due to declining fertility rates among non- Hispanic blacks and non-Hispanic whites. As a result of this declining fertility, the non-Hispanic white share of the population has fallen since 1970, and the non-Hispanic black share of the population has increased only slightly.

Changes in racial and ethnic identification have also contributed to the increase in (measured) racial and ethnic diversity. These changes are most important for the Native American population, which has increased more in recent years than can be accounted for by deaths, births, immigration and improvements in census coverage. The rise in these numbers in this population group suggests that people are more likely to identify themselves as Native Americans in the census than they were in the past.

National changes in the composition of the population mask differences across and within regions. The geographical distribution of racial and ethnic groups is important because it influences the potential for social and economic interaction between them. According to 1995 Census Bureau projections, the West had the highest concentration of minorities (36 percent), followed by the South (30 percent), the Northeast (23 percent), and the Midwest (15 percent). Non-Hispanic blacks are most likely to live in the South, while Asians, Hispanics and Native Americans are most likely to live in the West.

Racial composition also varies from the center cities of metropolitan areas, to the suburbs just outside, to nonmetropolitan areas. Hispanics, blacks and Asians are more likely than non-Hispanic whites to live in central cities (in 1996 more than half of blacks and Hispanics and nearly half of Asians lived in central cities, compared with less than a quarter of non-Hispanic whites). By contrast, over half of all non-Hispanic whites lived in the suburbs in 1996, as did 48 percent of Asians. Native Americans are by far most likely to live outside cities and suburbs; in 1990 nearly half of the American Indian population lived outside of metropolitan areas.

As the population becomes more diverse, opportunities for social interaction with members of other racial and ethnic groups should increase. Intergroup marriage (marriage between persons of different races or Hispanic origin) is one measure of social interaction. The number of interracial married couples (marriage between persons of different races) has increased dramatically over the past several decades, more than tripling since 1960. Yet a 1995 study by Roderick Harrison and Claudette Bennett found that interracial married couples still represented only about two percent, and intergroup couples four percent, of all married couples in 1990.

Many demographic characteristics affect economic and social status and play a role in explaining differentials in well-being among the U.S. citizenry. For instance, immigration has lowered the relative socioeconomic status of the U.S. Hispanic population, since Hispanic immigrants tend to have lower levels of education and income than the Hispanic population as a whole.

Other demographic characteristics with important effects on social and economic status include household structure and age distribution. In particular, growth of child poverty has often been associated with the rising share of single-parent families. Since 1970 the fraction of families maintained by a single parent has increased for all groups, and is highest among African Americans (38 percent), Native Americans (26 percent), and Hispanics (26 percent). Household structure is also affected by economic status; for example, the greater tendency of the elderly to head their own households has been linked to their increasing wealth.

Differences in the age distribution of populations may affect their rates of growth, as do differences in average economic and social well-being. For example, poverty rates are highest among children, and rates of criminal activity are highest among young adults. On average, the non-Hispanic white population is considerably older than the population as a whole. Only 24 percent of the non-Hispanic white population is below the age of 18, compared with about 30 percent of non-Hispanic blacks and Asians and about 35 percent of Native Americans and Hispanics. Differences in age distributions between racial and ethnic groups reflect differences in death rates, fertility rates, rates of net immigration and the age of immigrants.

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This article was excerpted from the second chapter of Changing America: Indicators of Social and Economic Well-Being by Race and Hispanic Origin, published by the Council of Economic Advisers for the President's Initiative on Race, September 1998.