New Estimates of the Undocumented Population
in the United States
By Jeffrey Passel
About 8.5 million undocumented immigrants lived in the United States in 2000, according to the best available evidence from estimates that combine data from Census 2000, the Immigration and Naturalization Service, the March 2000 Current Population Survey, the Census 2000 Supplementary Survey, and previous estimates.
This figure represents an increase of about 5 million over the estimates for 1990, leading to the conclusion that the annual increase during the 1990s averaged about 500,000. Both the total number of undocumented immigrants and the annual increase are considerably higher than estimates available before 2001.
Revising Earlier Estimates
Prior to the release of data from Census 2000, there had been a widespread consensus that the undocumented population in the United States was in a rough range of 5-6 million and was increasing by 200,000-300,000 per year. The results of Census 2000 shattered this consensus as the population count of 281.4 million exceeded pre-census estimates by 5-7 million. Detailed examination of these results by demographers within the Census Bureau and elsewhere led to the conclusion that the two main sources of the high count were improved census coverage overall, and underestimation of undocumented immigration during the decade of the 1990s.
Given the preliminary nature of the estimates and the lack of detailed data on the immigrant population from Census 2000, conclusions about the nature of undocumented immigration must remain tentative. However, several factors are clearly at work. First, a successful public relations campaign surrounding Census 2000 convinced many people to participate in the census who had not been covered in previous censuses and surveys. This factor seems to have especially affected undocumented immigrants who had been in the US for some time. In addition, there appears to have been an increase in the inflow of undocumented immigrants in the late 1990s, drawn by the very successful US economy.
Sources of Undocumented
| How Are These New Numbers Calculated? |
| The methods used to develop the estimates presented are a variant of the so-called "residual" methods that have been used for almost two decades to estimate the undocumented population of the United States, beginning with Warren and Passel's work on the 1980 Census. The method essentially involves estimating the legally-resident immigrant population counted in the census using data on legal inflows from the INS, the State Department, and the Office of Refugee Resettlement together with estimates of mortality, emigration, and migration within the country.
These estimates are subtracted from the total immigrant population counted in the census (derived by excluding estimated temporary immigrants from the count) to derive an estimate of undocumented immigrants counted in the census. This subtraction step is necessary because the census data do not identify the legal status of immigrants.
Finally, using information from coverage measurement programs and various non-census sources, assumptions are made about the number of undocumented immigrants omitted from the census to arrive at an estimate of the total undocumented population. (Note: These residual estimates of the undocumented population represent any immigrants who have not been legally admitted to the U.S. as permanent residents, legal temporary immigrants, refugees, asylees, or parolees. Some individuals and groups who fall into this residual are entitled to be in the country temporarily and are not strictly deportable; some examples include asylum applicants and those with temporary protected status. These groups may represent several hundred thousand people or more.)
As in previous eras, Mexican and other Latin American countries account for a significant majority of the total undocumented population. Mexicans alone represent about 4.7 million or 55 percent of the total undocumented population. The rest of Latin America accounts for another 22 percent or just under 2 million undocumented immigrants, so that undocumented immigrants of Latino origin represent about three-quarters of the total. Continental Asia, from Turkey to the Philippines, has sent slightly more than 1 million undocumented immigrants.
Estimates for specific countries other than Mexico must remain provisional at this point since the requisite census data on specific countries has not been released, but some inferences can be made. Among Latin American countries, the largest sources other than Mexico are probably El Salvador, Guatemala, Peru, Colombia, and the Dominican Republic, each accounting for 100,000?300,000. From Asia, the principal sources of undocumented immigration appear to be the same countries that send the largest numbers of legal immigrants -- India, China, Korea, and the Philippines. Contrary to published reports that misinterpreted Census Bureau estimates, there do not appear to be significant numbers of undocumented immigrants from the Middle East (i.e., Arab countries of southwest Asia, Iran, and Turkey).
Destinations of Undocumented Immigrants
Consistent with previous years and not unexpectedly, California is estimated to have the largest undocumented immigrant population -- about 2.3 million or just under one-quarter of the total. Then follows Texas (1.2 million), New York and Florida (roughly 700,000 each), Illinois (500,000), and New Jersey (300,000). These top six states (which have almost 70 percent of all immigrants) have about two-thirds of the undocumented population, or 5.7 million. The remaining 44 states and the District of Columbia have about 2.9 million undocumented immigrants, or about one-third of the total.
While this pattern is not unexpected, it does represent a qualitative change in settlement patterns. Undocumented immigrants appear to have joined other immigrants in spreading over more regions of the country. Most estimates for the mid-1990s and earlier showed upwards of 40 percent of undocumented immigrants in California, and more than 80 percent in these top six states. The dispersal of undocumented immigrants throughout the country follows trends identified by Passel and Zimmermann, who noted that a higher proportion of all new immigrants in the late 1990s were settling in 'new destination' states away from these traditional settlement areas. In addition, immigrants who were already in the country were moving to the new destinations in greater numbers. Since this new settlement pattern is being led by Mexican immigrants, it is not at all surprising to find significant undocumented populations in these new areas.
As with the detailed estimates for countries, the estimates for other states are somewhat tentative, since the detailed census figures required to produce the estimates are not yet available. The major destinations beyond the top six states are Arizona (more than 200,000), Georgia, Massachusetts, North Carolina, Washington, Virginia, Maryland, and Colorado (all in excess of 100,000). All of these except Washington and Massachusetts are among the 'new destination' states. Many other states have significant numbers and proportions of undocumented immigrants, but simply not enough immigrants to have more than 100,000 undocumented.
Foreign-Born Population Composition
The 8.5 million undocumented immigrants represent slightly more than one-quarter of the approximately 32 million immigrants in the United States in 2000. Among immigrants admitted as legal permanent residents, roughly as many have chosen to become US citizens through naturalization as have remained as noncitizens -- slightly less than 10 million each. About 7 percent of immigrants (2.3 million) have been admitted for humanitarian reasons as refugees, asylees, or similar groups. The remaining 1.5 million foreign-born residents have legal temporary statuses such as foreign students (F and M visas) and temporary workers (H-1B and L visas, for example).
Undocumented Immigrant Inflows
With the methods presented here, inflows of undocumented immigrants must be inferred. The estimates show that more than 6 million of the undocumented immigrants entered the US during the 1990s. During the last half of the decade, more than 700,000 per year came to the United States. This figure represents the inflow of undocumented immigrants, not the net flow of undocumented immigrants, as many depart every year and others become legal or die. The available estimates suggest that the undocumented population in 1990 was roughly 3.5 million. Thus, the change from 3.5 to 8.5 million implies an average annual net increase of 500,000, but all of the evidence points to larger increases in the latter half of the decade.
The Mexican immigrant population in the US in 2000 illustrates the nature of the inflows and changes during the 1990s. There are more than 9 million Mexican immigrants living in the United States and more than half are undocumented. However, the composition of entry cohorts varies widely -- the longer a group has been in the US, the higher the percentage of legal immigrants. Of the roughly 5 million Mexican immigrants who arrived in the US during the 1990s, about 80 percent are undocumented. Of the roughly 2.5 million arriving in the 1980s, less than 20 percent are undocumented and most of them arrived after 1986. Less than 10 percent of the pre-1980 entrants from Mexico remain undocumented. Similar patterns can be found among all groups, but Mexicans have the highest proportion undocumented.
Present and Future Trends
My initial estimates using data from the March 2001 Current Population Survey (CPS), not shown here, suggest that the trends noted above are continuing after Census 2000. The increase implied between the March 2000 and March 2001 CPS would put the undocumented population at over 9 million. There are reasons to expect a slowdown in growth or even a decrease in the undocumented population after March 2001 and the events of September 11, as life has become more difficult for all immigrants, and as the economy has slowed. However, we must await new data from 2002 to assess the impact of September 11 and the recession on trends in the undocumented immigration.
Jeffrey S. Passel is Principal Research Associate in the Immigration Studies Program at the Urban Institute in Washington, D.C. He has studied methods of measuring undocumented immigration since the late 1970s and has produced estimates of undocumented immigrants using the 1980, 1990, and 2000 Census and CPS data from 1983, 1986, 1988, 1991, and 1995 through 2001.
Back to the top
If you have questions or comments about this article, contact us at