Illegal Alien Resident Population 

Summary

About 5.0 million undocumented immigrants were residing in the United States in October 1996, 

with a range of about 4.6 to 5.4 million (See Table 1). The population was estimated to be growing 

by about 275,000 each year, which is about 25,000 lower than the annual level of growth estimated 

by the INS in 1994.

 

California is the leading state of residence, with 2.0 million, or 40 percent of the undocumented 

population. The 7 states with the largest estimated numbers of undocumented immigrants--

California (2.0 million), Texas (700,000), New York (540,000), Florida (350,000), Illinois (290,000), 

New Jersey (135,000), and Arizona (115,000)--accounted for 83 percent of the total population in 

October 1996. 

The 5.0 million undocumented immigrants made up about 1.9 percent of the total U.S. population, 

with the highest percentages in California, the District of Columbia, and Texas. In the majority of 

states, undocumented residents comprise less than 1 percent of the population.

Mexico is the leading country of origin, with 2.7 million, or 54 percent, of the population. The 

Mexican undocumented population has grown at an average annual level of just over 150,000 since 

1988. The 14 countries with 50,000 or more undocumented immigrants in 1996 accounted for 81 

percent of the total population. The large majority, over 80 percent, of all undocumented immigrants 

are from countries in the Western Hemisphere.

About 2.1 million, or 41 percent, of the total undocumented population in 1996 are nonimmigrant 

overstays. That is, they entered legally on a temporary basis and failed to depart. The proportion of 

the undocumented population who are overstays varies considerably by country of origin. About 16 

percent of the Mexican undocumented population are nonimmigrant overstays, compared to 26 

percent of those from Central America, and 91 percent from all other countries.

Background

In 1994 the INS released detailed estimates of the undocumented immigrant population residing in 

the United States as of October 1992.1 Those estimates were useful for a variety of purposes, 

including planning and policy development at the national and state level, evaluating the effects of 

proposed legislation, and assessing the fiscal impacts of undocumented immigration. 

The INS has revised those estimates and updated them to October 1996. The estimates presented 

here incorporate new data on the foreign-born population collected by the Census Bureau, 

improvements in the methodology recommended by the General Accounting Office (GAO), 

suggestions provided by outside reviewers, and further analyses of INS' data sources and estimation 

procedures. Revised and updated estimates of the undocumented population have been computed 

for each state of residence and for nearly 100 countries of origin.

Methodology

 

1 Warren, Robert. 1994, Estimates of the Unauthorized Immigrant Population Residing in the United 

States, by Country of Origin and State of Residence: October 1992, Unpublished Paper, U.S. 

Immigration and Naturalization Service.
The estimates were constructed by combining detailed statistics, by year of entry, for each 

component of change that contributes to the undocumented immigrant population residing in the 

United States. For most countries of the world, the typical way of entering the undocumented 

population in the United States is to arrive as a nonimmigrant and stay beyond the specified period 

of admission. This segment of the population, referred to here as "nonimmigrant overstays", 

constitutes roughly 40 percent of the undocumented immigrant population residing in the United 

States. The rest of the population, more widely publicized, enter surreptitiously across land 

borders, usually between official ports of entry. This part of the population, often referred to as 

EWIs (entry without inspection), includes persons from nearly every country, but a large majority of 

them are from Mexico; most of the rest are natives of Central American countries.

Primary Sets of Data

The figures presented here were constructed from five primary sets of data. Each set of data was 

compiled separately for 99 countries and each continent of origin. 

1) Entered before 1982--estimates (as of October 1988) of the undocumented immigrant population 

who established residence in the United States before 1982 and did not legalize under the 

Immigration Reform and Control Act (IRCA) of 1986. The assumption used to estimate this part of the 

population is based on estimates developed by the Census Bureau using data from the June 1988 

Current Population Survey (CPS). 

2) Net overstays--estimates for 1982 to 1996 of the net number of nonimmigrant overstays, for 99 

countries of origin, derived from INS data bases. Estimates were derived by: a) matching INS I-94 

arrival/departure records; b) adjusting for the incomplete collection of departure forms; and c) 

subtracting the number of nonimmigrant overstays who subsequently either departed or adjusted to 

legal resident status.

3) Net EWIs--estimates of the number from each country who entered without inspection (EWI) and 

established residence here between 1982 and 1996. A very large majority of all EWIs are from 

Mexico. Average annual estimates of Mexican EWIs were derived by: a) adjusting the CPS count 

of the Mexican-born population for underenumeration; b) subtracting the estimated legally resident 

population counted in the CPS; and c) subtracting the estimated number of net overstays. 

4) Mortality--estimates of the annual number of deaths to the resident undocumented immigrant 

population. The estimates were derived using an annual crude death rate of 3.9 per 1,000, which 

was computed using a modified age distribution of IRCA applicants and age-specific death rates of 

the foreign-born population.

5) Emigration--estimates of the number of undocumented immigrants who resided here at the 

beginning of a period (either October 1988 or October 1992), and who emigrated from the United 

States in the following 4-year period. Estimates of emigration are based on statistics published by 

the Census Bureau in Technical Paper No. 9.

Construction of the Estimates

Estimates of the undocumented immigrant population were derived for October 1988, October 1992, 

and October 1996 for 99 individual countries and for each continent of origin. The calculations were 

carried out separately for overstays and EWIs. 

Estimates by State of Residence

In the earlier estimates for October 1992, the state distribution of the undocumented population was 

based on the U.S. residence pattern of each country's applicants for legalization under IRCA; the 
results were summed to obtain state totals. This assumed that, for each country of origin, 

undocumented immigrants who resided in the United States in October 1992 had the same U.S. 

residence pattern as IRCA applicants from that country. The revised and updated estimates 

presented here incorporate the same assumption for the October 1988 undocumented population. 

However, it was necessary to develop new methods of deriving state estimates for October 1992 

and 1996 that would reflect more recent patterns of geographic settlement.

As noted, the estimates of the undocumented population were constructed separately for overstays 

and EWIs. This permitted the distribution of the overstay and EWI populations to states using data 

most appropriate for the type of population. For overstays, the cohorts that arrived in the 1988-92 

and 1992-96 periods were distributed to state of residence based on annual estimates of overstays 

by state of destination for 1986 to 1989. For EWIs who entered during these periods, the totals 

were distributed to state of residence using INS statistics for the early 1990s on the destination of 

the beneficiaries of aliens who legalized under IRCA. 

Limitations

Estimating the size of a hidden population is inherently difficult. Overall, the figures presented here 

generally reflect the size, origin, and geographic distribution of the undocumented immigrant 

population residing in the United States during the mid-1990s. The estimates probably reduce the 

range of error for the total population to a few hundred thousand rather than a few million, which was 

the error range during the late 1970s and into the 1980s. The estimates for most countries should 

be fairly precise because they were constructed primarily from data on nonimmigrant arrivals, 

departures, and adjustments of status that have relatively small margins of error.

Although the estimates are based on the most reliable information available, they clearly have 

limitations. For example, the estimates make no allowance for students or other long-term 

nonimmigrants, and the estimates for some countries could be underestimated because of special 

circumstances (e.g., Dominicans entering illegally via Puerto Rico; ships arriving undetected from 

China). 

The figures for some countries overstate the actual undocumented population. In general, the net 

nonimmigrant overstay figures are more likely to be overestimates than underestimates because the 

collection of departure forms for long-term overstays who depart probably is less complete than for 

those who depart within the first year. 

The estimates include a large number of persons who have not been admitted for lawful permanent 

residence but are permitted to remain in the United States pending the determination of their status 

or until conditions improve in their country of origin. This category includes many of the 

undocumented immigrants from El Salvador, aliens from other countries in a status referred to as 

"deferred enforced departure", and IRCA applicants whose cases have not been finally resolved.

The number of EWIs is the most difficult component to estimate with precision, and errors in this 

component have the largest effect on the estimated undocumented population from Mexico. In 

particular, the shortage of information about two components--emigration of legally resident 

immigrants and undercount in the CPS--makes it difficult to derive acceptable residual estimates of 

the number of undocumented immigrants counted in the CPS.

The estimates presented here are based on the most extensive array of figures ever compiled for the 

purpose; nevertheless, they should be used with caution because of the inherent limitations in the 

data available for estimating the undocumented immigrant population. This uncertainty was 

addressed by using alternative assumptions to produce "high" and "low" population estimates for 

October 1996. In the following discussion of the estimates, the mid-range population figures are 

used for simplicity of presentation. 
Results

National Estimates

The total number of undocumented immigrants residing in the United States in October 1996 is 

estimated to be 5.0 million (See Table 1), with a range of about 4.6 to 5.4 million. The estimate for 

October 1996 is about 1.1 million higher than the revised estimate of 3.9 million for October 1992; 

this implies that the population grew by about 275,000 annually during the 1992-96 period, about the 

same as the annual growth of 281,000 estimated for the previ ous period. The original INS estimates 

for October 1992 and October 1988, released in 1994, showed average annual growth of 300,000.

The undocumented population grows at varying levels from year to year, but the data available to 

make these estimates do not permit the derivation of annual figures to measure year-to-year 

changes. However, the similar levels of growth for the 1988-92 and 1992-96 periods, 281,000 and 

275,000, respectively, suggest that the overall level of growth has been fairly constant over the past 

decade. This also indicates that the rate of growth of the undocumented resident population has 

declined since 1988.

State of Residence

The estimates for states reflect the well-established pattern of geographic concentration of 

undocumented immigrants in the United States. As expected, California was the leading state of 

residence, with 2.0 million, or 40 percent, of the total number of undocumented residents in October 

1996. Seven states--California (2.0 million), Texas (700,000), New York (540,000), Florida 

(350,000), Illinois (290,000), New Jersey (135,000), and Arizona (115,000)--accounted for 83 percent 

of the population in October 1996 (See Table 1). 

The estimated undocumented population of California has grown by an average of about 100,000 

annually since the end of the IRCA legalization program in 1988. More than 83 percent of total 

growth of the undocumented population since 1988 has occurred in the top seven states. With the 

exception of Massachusetts (6,000), none of the remaining 43 states grew by more than 3,000 

undocumented residents annually. In 27 states, the undocumented population grew by an average 

of 1,000 or less each year. 

Country of Origin

Mexico is the leading source country of undocumented immigration to the United States. In 

October 1996 an estimated 2.7 million undocumented immigrants from Mexico had established 

residence here (See Table 1). Mexican undocumented immigrants constituted about 54 percent of 

the total undocumented population. The estimated population from Mexico increased by just over 

150,000 annually in both the 1988-92 and 1992-96 periods. 

The estimated number of Mexican undocumented immigrants who arrived between 1990 and 1996 is 

based on data on country of birth and year of immigration collected by the Census Bureau in the 

March 1994, 1995, and 1996 Current Population Surveys (CPS). Demographic analysis of the CPS 

data indicates that approximately 230,000 undocumented Mexican immigrants established 

residence annually between 1990 and 1996. This is the net annual addition of undocumented 

Mexicans who arrived during the period. Note, however, that it does not reflect the average annual 

growth of the Mexican undocumented population. To compute average annual growth it is 

necessary to subtract the number of undocumented Mexicans who lived here in January 1990 and 

who emigrated, died, or adjusted to legal permanent resident status during the 1990-96 period. This 
last step produces the estimate cited above of just over 150,000 annual growth of the Mexican 

undocumented population since 1988. 

In October 1996, 15 countries were each the source of 40,000 or more undocumented immigrants 

(See Table 1). The top five countries are geographically close to the United States--Mexico, El 

Salvador, Guatemala, Canada, and Haiti. Of the top 15 countries, only the Philippines, Poland, and 

Pakistan are outside the Western Hemisphere. The estimated undocumented population from 

Poland has declined by more than 25 percent, from 95,000 to 70,000, since 1988, possibly 

reflecting changed conditions in that country over the last several years.

Although undocumented immigrants come to the United States from all countries the world, 

relatively few countries add substantially to the population. The annual growth of the undocumented 

population can be grouped into four disparate categories: 1) Mexico, with more than half of the 

annual growth, adds just over 150,000 undocumented residents each year; 2) six countries--El 

Salvador, Guatemala, Canada, Haiti, Honduras, and the Dominican Republic--each add between 

6,000 and 12,000 annually; 3) thirteen countries each add about 2,000 to 4,000 annually; and 4) the 

remaining approximately 200 other countries add a total of about 30,000 undocumented residents 

each year (See Table 1). A large majority of the additions each year, more than 80 percent, are 

from countries in the Western Hemisphere. 
Table 1.

Estimated Illegal Immigrant Population for Top Twenty Countries of Origin

and Top Twenty States of Residence: October 1996

Country of origin Population State of residence Population

All countries 5,000,000 All states 5,000,000

1. Mexico 2,700,000 1. California 2,000,000

2. El Salvador 335,000 2. Texas 700,000

3. Guatemala 165,000 3. New York 540,000

4. Canada 120,000 4. Florida 350,000

5. Haiti 105,000 5. Illinois 290,000

6. Philippines 95,000 6. New Jersey 135,000

7. Honduras 90,000 7. Arizona 115,000

8. Dominican Republic 275,000 8. Massachusetts 85,000

9. Nicaragua 70,000 9. Virginia 55,000

10. Poland 70,000 10. Washington 52,000

11. Colombia 65,000 11. Colorado 45,000

12. Ecuador 55,000 12. Maryland 44,000

13. Trinidad & Tobago 50,000 13. Michigan 37,000

14. Jamaica 50,000 14. Pennsylvania 37,000

15. Pakistan 41,000 15. New Mexico 37,000

16. India 33,000 16. Oregon 33,000

17. Ireland 30,000 17. Georgia 32,000

18. Korea 30,000 18. District of Columbia 30,000

19. Peru 30,000 19. Connecticut 29,000

20. Portugal 27,000 20. Nevada 24,000

Other 764,000 Other 330,000

 

2

 The estimated illegal immigrant population from the Dominican Republic was revised 

from 50,000 in an earlier version of this document to 75,000 following a review of the 

estimates for Dominica and the Dominican Republic.