Homeward Bound: Recent Immigration Enforcement and the Decline in the Illegal Alien Population

By Steven A. Camarota and Karen Zeigler on July 30, 2008

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Monthly data collected by the Census Bureau through May 2008 shows a significant decline in the number of less-educated, young Hispanic immigrants in the country. The evidence indicates that the illegal immigrant population may have declined by over one million in the last year. There are strong indications immigration enforcement is responsible for at least part of the decline. The economy also is likely playing a role.

Among the findings:

  • Our best estimate is that the illegal immigrant population has declined by 11 percent through May 2008 after hitting a peak in August 2007.
  • The implied decline in the illegal population is 1.3 million since last summer, from 12.5 million to 11.2 million today.
  • The estimated decline of the illegal population is at least seven times larger than the number of illegal aliens removed by the government in the last 10 months, so most of the decline is due to illegal immigrants leaving the country on their own.
  • One indication that stepped-up enforcement is responsible for the decline is that only the illegal immigrant population seems to be affected; the legal immigrant population continues to grow.
  • Another indication enforcement is causing the decline is that the illegal immigrant population began falling before there was a significant rise in their unemployment rate.
  • The importance of enforcement is also suggested by the fact that the current decline is already significantly larger than the decline during the last recession, and officially the country has not yet entered a recession.
  • While the decline began before unemployment rose, the evidence indicates that unemployment has increased among illegal immigrants, so the economic slow-down is likely to be at least partly responsible for the decline in the number of illegal immigrants.
  • There is good evidence that the illegal population grew last summer while Congress was considering legalizing illegal immigrants. When that legislation failed to pass, the illegal population began to fall almost immediately.
  • If the decline were sustained, it would reduce the illegal population by one-half in the next five years.


There is widespread agreement that, until recently, immigration laws have been largely unenforced within the United States. However, there is a long-standing debate over whether enforcing immigration laws would significantly reduce the number of illegal immigrants. Some have argued that because illegal immigrants are so firmly embedded in American society, enforcement would not significantly reduce their numbers. It is also argued that the desire to immigrate to the United States is so strong that enforcement could not deter illegal immigrants from coming.

This study analyses the Current Population Survey (CPS) collected monthly by the Census Bureau. The findings show clear evidence that the illegal population has declined significantly. The evidence indicates that, since hitting a peak in the summer of 2007, the illegal population may have declined by 11 percent through May of 2008. It seems that increased enforcement is at least partly responsible for this decline.

These findings are consistent with anecdotal evidence.1 They also are consistent with data showing some decline in remittances sent home by immigrants.2 And they are in line with a drop in border apprehensions.3 Future enforcement efforts as well as the state of the economy will likely determine if the current trend continues. Both presidential candidates have repeatedly stated their strong desire to legalize those in the country illegally. Such pronouncements may encourage illegal immigrants to remain in the county in the hope of qualifying for a future amnesty. It may also encourage more illegal immigration. So it is far from certain that the current trend will continue. Moreover, it must be remembered that the illegal population remains very large. We estimate that the illegal population stood at 11.2 million in May 2008. While down from our estimate of 12.5 million in August 2007, the illegal population is still extremely large.

New Enforcement Efforts. When efforts to legalize illegal immigrants failed in the U.S. Senate last summer, Secretary of Homeland Security Michael Chertoff and Commerce Secretary Carlos Gutierrez stated that, “until Congress chooses to act, we’re going to be taking some energetic steps of our own.”4 They emphasized that in addition to better policing of the border, the government was also going to do more in terms of interior enforcement, particularly pursuing employers who hire illegals.

Even before the legalization was defeated in June 2007, the administration was doing much more to enforce the law. The fenced portion of the U.S. border has increased significantly in the last 18 months and the number of Border Patrol agents has more than doubled in recent years to over 16,500. The number of detention beds used to hold aliens has more than doubled since 2000 to over 30,000. In 2007, 426 local law enforcement personnel participated in the 287(g) program, which trains police and allows them to enforce immigration laws.5 The number of aliens removed (including deportations) has increased significantly in recent years. In 2007, 285,000 aliens were removed, nearly double the number in 2002.6 Immigration and Customs Enforcement is likely to match its 2007 total through 2008.7

The E-Verify program, which allows employers to screen workers to see if they are authorized to work in the country, now covers about one out of 10 new hires in the country.8 Worksite enforcement has seen some of the largest increases in recent years, with the number of criminal and administrative arrests increasing more than five-fold since 2004.9

In many ways these efforts are still quite modest, and represent large relative increases from what was a very low level of enforcement. Nonetheless, they do constitute a more comprehensive approach to enforcement, both at the border and within the United States. They also represent a significant departure from a policy of non-enforcement during the Clinton administration and most of the Bush administration.

State and Local Enforcement Efforts. Over the past year, many state and local governments have acted to buttress federal efforts to enforce immigration laws. A good deal of debate has typically surrounded these proposals. Even when such initiatives fail to pass a state legislature or city council, local media, particularly foreign-language media, often cover these debates extensively. And while most proposals have not passed, some significant measures have been adopted. These include Georgia, Missouri, Arizona, and Oklahoma, which now require some employers to use the E-Verify system in order to obtain business licenses or government contracts. They also include increased efforts to use local police to enforce immigration laws. Some local governments have even tried to make it illegal for landlords to rent homes to those in the country illegally.

Some of these initiatives are likely to be tied up in the courts for years, and the overall effectiveness of state and local enforcement efforts can be debated. However, these efforts do have the effect of conveying to illegal immigrants and perhaps their employers that enforcement is not only increasing, but that enforcement resources are growing. And that the federal government is no longer the only factor to consider. In such an environment, a larger share of illegal immigrants may decide to leave the country. This is especially true given the large amount of coverage these initiatives receive in Spanish-language media, which covers even modest enforcement actions.


Recent Trends. Figure 1 shows the number of foreign-born adults living in the country between January 2005 and May 2008 based on the Current Population Survey (CPS). The figure reflects a three-month moving average.10 In this report we use the terms “immigrant” and “foreign-born” synonymously.11 We also use the terms “illegal immigrant” and “illegal alien” interchangeably.12 The lower line in Figure 1, which corresponds to the right axis, shows the number of adult Hispanic immigrants 18 to 40 years of age with a high school degree or less living in the United States. We estimate that three-fourths of these young, less-educated foreign-born Hispanics are illegal aliens and that roughly two-thirds of all adult illegal aliens are young, less-educated Hispanics. These estimates are consistent with a large body of research showing that illegal aliens are overwhelmingly Hispanic, young, and have relatively few years of schooling.13 This population of less-educated young Hispanic immigrants can be seen as the likely illegal immigrant population. The top line shows the remainder of the adult immigrant population or the likely legal immigrant population. Examining these two proxy populations in this way provides a great deal of insight into trends in the size and growth of the legal and illegal immigrant populations.


Adult Immigrants Jan 2005 to May 2008


It must be remembered that there is always a significant amount of turnover in both of these populations. New immigrants (legal and illegal) arrive from abroad and some immigrants already in the country die or return to their home countries. Since the death rate remained virtually unchanged over the time period of this study, a sudden decline in one or both of these populations would mean that more people are leaving the country than are coming into the country. If it was only the case that fewer immigrants were coming, but those already in the country were not leaving, the total population should not fall suddenly. Instead, it would grow little or not at all or decline slowly. We will return to the question of immigrants coming and going later in this report. What is important about the figures is that they show total populations, which represent the cumulative effect of in-migration and out-migration.

A Decline in the Illegal Population. Figure 1 indicates that after peaking last summer, the likely illegal population declined significantly. If we compare the peak in August 2007 with May 2008 we find that the likely illegal immigrant population fell about 11 percent. This is a substantial decline and corresponds with stepped-up immigration enforcement efforts. It also corresponds to the failure to pass legislation that would have legalized most illegal aliens. That legislation failed for the final time on June 28, 2007. The top line in Figure 1 indicates that the number of likely legal immigrants in the country did not decline in a similar fashion. Although both legal and illegal immigrants are subject to the economic downturn, it seems that only the illegal immigrant population is declining. This is consistent with the idea that the enforcement of immigration laws is causing the decline. Of course, less-educated workers in general are more vulnerable to hardship during an economic downturn than are more-educated individuals. This fact may also partly explain why the number of less-educated, young Hispanics immigrants fell while the rest of the adult immigrant population did not fall in the same way.

The Economy vs. Enforcement. Figure 2 shows the likely illegal population and its unemployment rate. The figure shows that the recent fall in the number of less-educated, young, foreign-born Hispanics began before there was a significant jump in their unemployment rate.14 This suggests that the fall in the size of the likely illegal population was caused by enforcement rather than deterioration in the economy. However, the rise in unemployment now may be acting in concert with increased enforcement efforts, making it increasingly difficult to determine the relative importance of the economy or enforcement if the current decline continues. One factor that makes it difficult to weigh the relative importance of the economy vs. enforcement is that a rise in the unemployment rate also may be partly caused by an increase in enforcement efforts as states and the federal government make it more difficult for illegal immigrants to find or retain jobs.


Graph: Number and Unemployment Rate of Less Educated  Adult Hispanic Immigrants, January 2005 to May 2008


Figure 3 shows the unemployment rate of the likely legal immigrant population. While unemployment has risen for this group, there is no indication that its numbers are falling. This suggests that the difference between the illegal and legal immigrant populations is the increased enforcement that illegal immigrants are experiencing. However, it must be pointed out that the increase in unemployment for the likely illegal population was much larger than it was for the legal immigrant population. So this may also explain the divergent trend between these two populations. Since the decline in the number of less-educated Hispanics began before there was a significant increase in their unemployment rate, it seems that at least initially the decline was due to factors other than the economy.


Graph: Number and Unemployment Rate of Other Adult Immigrants, January 2005 to May 2008


Trends Since 2000. Figures 1, 2, and 3 all examine data from January 2005 to May 2008. Figures 4 and 5 show the likely legal and illegal populations from January 2000 to the present. Again, the figures use a three-month moving average to create robust estimates. The long-term trend shows fluctuations with several dips that imply a fall in the illegal population. While there is some debate about when the last recession began, the National Bureau of Economic Research reports that it began in March of 2001 and ended in November of that year. Figure 4 shows that the illegal population peaked in April 2001 and declined about 7 percent by September 2001. The second peak occurred in May 2002 followed by a 6 percent decline by September 2002. These swings in the illegal population seem to represent both the temporary increase in immigration enforcement that occurred after the 9/11 attacks and the effects of the 2001 recession. Another factor to consider is that in the months just prior to the 9/11 attacks, President Bush indicated his desire to legalize illegal immigrants from Mexico and perhaps elsewhere. This also could have impacted migration patterns by increasing the number of illegals who stayed and the number coming to the country.



Talk of an amnesty for illegal immigrants, the 2001 recession, and 9/11-inspired enforcement all make the years 2001 to 2003 difficult to interpret.15 In fact, the period from January 2001 to October 2003 shows one of the largest increases in the likely illegal population over the entire 2000 to 2008 period, despite some fluctuations. While Figure 4 is subject to different interpretations, in general it does show that when the unemployment rate among illegals increased, the size of the likely illegal population fell, at least somewhat. But there is a delayed effect. This was at least true for the rise in their unemployment rates in 2001 and 2002. This makes perfect sense because as illegal immigrants start losing their jobs, some decide to go home and fewer enter the country, but the effect is not immediate.

The decline in the size of the likely illegal population in March 2003 and March 2004 was much smaller than the decline associated with the earlier unemployment spikes of 2001 and 2002. Nevertheless, a rise in unemployment happened first, followed by a modest fall in the population of less-educated, young Hispanics. However, the current decline does not fit this pattern. As we have seen, the current decline clearly began before unemployment rose significantly. This is consistent with the idea that enforcement has played a significant role in the fall-off in the illegal population.

Failure of the Immigration Legalization. One of the more interesting findings in the figures is the rise or “hump” in the likely illegal immigrant population last summer. This hump may have been associated with the congressional debate over granting legal status/amnesty to illegal immigrants. The number of less-educated, young Hispanics hit a high in August 2007. The bill and its legalization provisions were widely covered by both the English- and foreign-language media in the United States and received significant coverage in some foreign countries, particularly in Latin America. It is certainly possible that more illegal immigrants settled in the country during the debate and fewer went home than otherwise would have been the case. Illegals may have hoped that by coming to or remaining in the country they would qualify for the legalization. The bill failed to pass at the very end of June 2007, and although there was some talk of bringing the legislation up again, after August the size of the less-educated Hispanic population began to fall significantly. There is, of course, a seasonable component to illegal immigration, but what might be called the “amnesty hump” does not seem to exist in prior years. So it is certainly plausible that this rise and fall was due to the congressional debate over amnesty and then the failure of the legislation to pass.

Immigrants Coming and Going. The figures show only the total number of likely legal and illegal immigrants in the country. As already discussed, the observed decline must be due to a combination of less-educated, young Hispanic immigrants leaving the country and fewer entering the country. Below we estimate the relative importance of these two factors. In this discussion it should be remembered that none of the figures are adjusted for undercount in the CPS. This issue will be dealt with in the next section of this report. The figures also do not include children.

Individuals can drop out of the population of less-educated, young Hispanic immigrants by leaving the country, turning 41, dying, or by increasing their education. The CPS indicates that the number of individuals aging out of this population from August 2007 to May 2008 was 290,000. The number of deaths was, at most, 10,000. We also estimate that 50,000 of these individuals became more educated. Thus, the total estimate for the number leaving this population by dying, aging out, or becoming more educated is 350,000 over the 10-month period from August 2007 to May 2008. This is offset by 150,000 new individuals aging into this population by turning 18 during this time period. Therefore, the decline in this population would have been about 200,000 (350,000 minus 150,000) if no new immigrants had arrived from aboard. This 200,000 can be seen as the natural decline in this population over time, assuming no new immigrants come from abroad and none leave the country. The actual decline from August 2007 to May 2008 was 820,000. This means that most of the decline was caused by likely illegal aliens leaving the country. This is especially true when we consider that some number of new immigrants arrived from abroad.

Because of the way the Census Bureau groups data in the public use file of the CPS, it is difficult to precisely estimate the number of new immigrants arriving from abroad in a single year. However, our best estimate for the number of likely illegal immigrants arriving from abroad in the year prior to August 2007 is 300,000. In the year prior to 2008 we estimate 220,000 new less-educated, young Hispanic immigrants arrived from abroad.16 This suggests that the number of new arrivals may have declined by perhaps one-fourth since summer 2007.17 Taken together, these results indicate that the natural decline (200,000) in the likely illegal population coupled with the additions caused by the arrival of new immigrants from abroad should have balanced out and created a population that was roughly stable in size between August 2007 and May 2008. Thus the 820,000 decline seems to have been caused almost entirely by the departure of likely illegal immigrants already in the country. Of course, if the number of new arrivals had been larger or smaller it would have changed the results. So it is also reasonable to argue that the fall in illegal immigration shown in the figures was caused by both fewer immigrants coming and more leaving. But the predominate factor seems to be a significant rise in out-migration.

Immigration and Customs Enforcement reports that they removed 176,000 aliens from the United States between September 2007 and the beginning of July 2008.18 Not all of these individuals were illegally in the country; many had green cards and thus were not illegal aliens. Moreover, the figures also include individuals who were prevented from entering the country at a port of entry and, therefore, were never part of the illegal population residing in the country and would not have shown up in the estimates presented here. But what is important about these numbers is that the 176,000 figure is substantially less than the estimated decline in the illegal population. This means that many more illegal immigrants left the country on their own, rather than having been made to do so by the government. This strongly implies that if the United States were to decide to substantially reduce the illegal population through enforcement, it would not be necessary to deport every single person who is in the country illegally. The evidence indicates that illegal immigrants respond to changing incentives and that many would return home on their own if they felt enforcement was a real possibility.

The Total Illegal Population. Although a number of institutions and organizations have tried to estimate the size of the illegal population, there is still some uncertainty about its actual size. The most recent estimates by the Department of Homeland Security show an illegal population of 11.55 million in January 2006.19 Based on the Current Population Survey, the number of adult, likely illegal aliens in January 2006 was 7.2 million. This is shown in Figures 1, 2, and 4. This creates a ratio of 1 to 1.6. It must be remembered that the illegal numbers published by DHS include an adjustment for undercount; Figures 1, 2, and 4 do not.

The DHS uses Census Bureau data to create its estimates, but they assume 10 percent of the illegal population is missed and adjusts its estimates upward by this amount.20 The government’s estimates also include nearly two million illegal alien children, which are not part of this study. If we assume that the ratio of 1 to 1.6 held constant, it means that the illegal-alien population peaked at 12.49 million in August 2007 and then fell to 11.17 million by May of 2008. These results are shown in Figure 6. This means that although the illegal immigrant population is falling, it remains very large. The results suggest that if the current trend were maintained for even five years, it would cut the illegal population by half.



Limitations of This Analysis. The estimates produced in this report are consistent with prior research. Nonetheless, there is always uncertainty when estimating the illegal population. There are two key limitations to the approach used in this report. First, while it is clear that a large share of illegal aliens are included in Census Bureau surveys, there is always the question of those who are missed. Although DHS as well as most researchers assume a 10 percent undercount, there is debate about the number of illegal immigrants who are not counted.21 In an environment of stepped-up enforcement, it is possible that the undercount could rise as a larger share of illegal immigrants become reluctant to answer a government survey. This in turn could create the illusion that the illegal population is falling when in fact the population remains unchanged. As mentioned above, the fall-off in the illegal population is certainly consistent with anecdotal evidence. It is also consistent with remittance data, border apprehensions, and some administrative data, such as school enrollment. Moreover, a fall-off of 11 percent is inherently plausible. There are also several technical factors concerning how the CPS is conducted that tend to prevent a sudden apparent decline in the illegal population due to an increase in non-response rates.22

A second limitation of the approach used in this study is that it does not provide much insight into the non-Hispanic illegal population. All researchers agree that the overwhelming majority of adult illegal aliens are Hispanic and that they are younger adults with relatively few years of schooling. Thus, we are confident that our approach captures trends in the Hispanic illegal population and the overall illegal population. We also are confident that it captures trends in the illegal child population, which is also overwhelmingly Hispanic. However, it is unclear what is happening to the other 20 percent of illegal immigrants who are primarily from East and South Asia.23 It is much harder to estimate a trend for these illegal immigrants using the CPS, primarily because they are a much smaller population. While it is reasonable to assume that their trends are similar to Hispanic illegal immigrants, we cannot say with certainty whether their population is declining in the same way.24


It is sometimes argued that illegal immigrants are so permanently attached to their lives in the United States that no amount of enforcement would ever make a large share of them return to their home countries. The findings of this report tend to contradict that view. Monthly data collected by the Census Bureau show a significant drop in the number of less-educated, young Hispanic immigrants in the country. Prior research indicates that more than three-fourths of these individuals are illegal aliens. The fall in this population implies that the illegal-immigrant population has declined some 11 percent or 1.3 million since hitting a peak in August 2007. The decline began before unemployment increased in this population, so increased enforcement seems to have played a significant role in reducing the illegal population. However, the deterioration in the economy also is likely to be partly responsible. The decline in the illegal population, whatever the cause, seems to directly challenge the argument that illegal aliens are here to stay and there is no way to induce many of them to return home. The evidence presented here suggests that it has been possible to cut the illegal population by inducing a large number to leave the country. In fact, if the current trend were sustained, it could cut the illegal population in half within just five years.

This study says nothing about whether the drop in illegal immigration is desirable. Our own view is that muscular enforcement of immigration laws is a vital part of any meaningful reform of our immigration system. However, some may feel that enforcement is a mean-spirited approach for people who come to the United States in search of a better life. Many also argue that the country needs these workers. The preferred solution of people who hold these views is that illegal immigrants be legalized and allowed to stay. But whatever one’s view on illegal immigration, the findings of this report show strong evidence that the illegal population has fallen significantly in the last year.

There is no way to know whether the current trend will continue. However, in recent weeks both presidential candidates have repeatedly indicated their deep commitment to legalizing those in the country illegally. Pronouncements of this kind have consequences. When Congress was considering legalization for illegal immigrants last summer, there is evidence that the illegal population grew. When the legislation failed to pass, the illegal population began to decline rapidly. It may be that the promises in recent weeks by both presidential candidates will again encourage more illegal immigrants to enter or encourage those already in the country, who might otherwise leave, to stay in the hopes of being awarded legal status. Many illegal immigrants who are thinking about leaving may now be taking a wait and see approach.

End Notes

1 A number of recent articles have reported on illegal immigrants leaving the country. An article in The New York Times from February 18 of this year, “Arizona Seeing Signs of Flight by Immigrants,” is typical of many news accounts of illegal immigrants going home. The article discussed a decline in school enrollment and rising apartment vacancy rates in Arizona. It also profiled illegal immigrants who are leaving the country. The article is similar to one from July 10, 2008, in The Washington Post, “Hispanic Population in Decline: Illegal Immigrant Policy Alters Prince William on Many Levels.” The article examined Prince William County in Virginia and its crackdown on illegal immigrants. It reported a large drop in school enrollment for non-English-speaking children and also a decline in customers at businesses that serve illegal aliens. Also see, “More Illegal Immigrants Putting Affairs in Order Deportation Risk Prompts Preparation,” The Washington Post, July 15, 2008.

2 A May 1, 2008, article in The New York Times, “Fewer Latino Immigrants Sending Money Home,” reported the following: The Inter-American Development Bank has reported that money transfers (remittances) to Latin America have either dropped, or there has been no growth. This reverses a five-year trend of increasing transfers. The Central Bank of Mexico reports that there has been a 2.9 percent drop in money transfers in the first quarter of 2008 compared to the first quarter of 2007. It should be noted that legal immigrants account for a significant share of money sent home by immigrants in this country. So remittances are an imperfect measure of illegal immigration at best.

3 Secretary of Homeland Security Michael Chertoff stated in Congressional testimony on April 2, 2008, to the Senate Committee on the Judiciary that there was a 20 percent decline in apprehensions across the southern border for fiscal year 2007. He also testified that during the first quarter of fiscal year 2008, southwest border apprehensions “were down 18 percent, and nationwide they were down 17 percent over the same period the previous year.” Mr. Chertoff argued that this is an indication that fewer illegal immigrants are attempting to enter the country. Apprehensions are an imperfect measure of illegal immigration: Between 30 and 40 percent of illegal immigrants originally entered the country legally and then overstayed a time-limited visa. And of course, there is also the issue of illegals who slip past the Border Patrol.

4 Press release dated August 10, 2007. http://www.dhs.gov/xnews/releases/pr_1186781502047.shtm

5 The 287(g) figures come form the 2007 ICE Annual Report, which can be found at: www.ice.gov/doclib/about/ice07ar_final.pdf

6 In 2002, 162,000 aliens were removed. See “Immigration Enforcement Actions: 2006, Annual Report,” www.dhs.gov/xlibrary/assets/statistics/publications/enforcement_ar_06.pdf.

7 Information provided by Immigration and Customs Office of Congressional Relations. These figures include expedited removals.

8 May 21, 2008, posting by Stewart Baker, Assistant Secretary for Policy at ICE, which can be found at: www.dhs.gov/journal/leadership/labels/E-Verify.html

9 In 2004, there were only 165 criminal arrests at work sites and 685 administrative arrests. This grew to 863 criminal arrests, and 4,077 administrative arrests at worksites by 2007. Through May of this year there have been 875 criminal arrests and 3,000 administrative arrests at worksites. See Homeland Leadership Journal, July 9, 2008, at www.dhs.gov/journal/leadership/

10 We focus on adults (18 and older), because the migration of children reflects the decision of their adult parents. We use a three-month moving average in an effort to overcome the natural volatility inherent in any survey. So, for example, the figures for February include December and January. The figures for March include January and February and so on. There are about 13,000 immigrant adults in each monthly CPS file, 2,500 to 3,000 of whom are young, less-educated Hispanics. The Census Bureau weights the survey to reflect the nation’s total population.

11 The foreign-born are defined as persons living in the United States who were not U.S. citizens at birth. This includes naturalized American citizens, legal permanent residents (green card holders), illegal aliens, and people on long-term temporary visas such as students or guest workers, who respond to the CPS. It does not include those born abroad of American parents or those born in outlying territories of the United States such as Puerto Rico.

12 Both terms refer to individuals who are living in the United States without proper authorization. Some have overstayed a temporary visa or other time-limited stay in the United States, while others have snuck into the country.

13 The Center for Immigration Studies has estimated that 81 percent of illegal aliens have no education beyond high school. We also estimate that 79 percent of adult illegal immigrants are Hispanic. The Center’s estimates of the characteristics of the illegal population can be found in “Immigrants in the United States, 2007: A profile of America’s Foreign-Born Population,” www.cis.org/immigrants_profile_2007. The most recent estimates from the Department of Homeland Security indicate that about 80 percent of illegal aliens are from Latin America. The report is entitled “Estimates of the Unauthorized Immigrant Population Residing in the United States” and can be found at www.dhs.gov/xlibrary/assets/statistics/publications/ill_pe_2006.pdf. In a recent series of studies, the Pew Hispanic Center has estimated that 78 to 81 percent of illegal aliens are from Latin America. In a 2005 report, Pew estimated that 75 percent of illegals had no education beyond high school (page 23), http://pewhispanic.org/files/reports/46.pdf . Older studies of the illegal population also have found similar percentages of illegals who have relatively little education and are Hispanic. The Urban Institute estimate of the illegal population in 2002 can be found at http://www.urban.org/url.cfm?ID=1000587. An older estimate by the INS can be found at http://www.dhs.gov/xlibrary/assets/statistics/publications/Ill_Report_12.... The Census Bureau estimate can be found at: www.census.gov/dmd/www/ReportRec2.htm (Appendix A of Report 1 contains the estimates). Both the INS and Census have found that the illegal population is at least 80 percent Hispanic.

14 The unemployment figures are not seasonally adjusted. They are a three-month moving average. We use unadjusted numbers so that the seasonality of immigrant employment can be observed. Seasonal adjustments smooth the rise and fall in unemployment.

15 It must be remembered that illegal immigrant employment is partly seasonal, with more in the country during the summer months when employment increases in agriculture, construction, and the hospitality industry.

16 All individuals in the CPS are asked what year they came to the United States. But in order to preserve anonymity, the Bureau groups responses into several-year cohorts. For example, in 2007 persons who said they arrived in 2004 through 2007 were coded as one response. Thus there is no real way to know for sure which individuals arrived in the year prior to the survey. However, it is possible to get some idea of the number of new arrivals by dividing the number of months into each cohort.

17 It is interesting to note that the August 2006 data indicate that there were 340,000 new illegal immigrants arriving from aboard in the year prior. This is larger than the 300,000 found in August 2007 and also is much larger than the 220,000 found in May 2008. These numbers imply that the number of new arrivals may have been falling for some time. Again, the difficulty in interpreting new arrival data from the CPS must be kept in mind.

18 Figures provide by Immigration and Customs Enforcement via email July 14, 2008.

19 See footnote 12 for Department of Homeland Security illegal estimates for 2006.

20 DHS uses the American Community Survey (ACS) collected by the Census Bureau. It is similar to the CPS and generally produces very similar estimates of the foreign born population. The ACS is not available on a monthly basis.

21 The Pew Hispanic Center assumes a 5.2 percent undercount of the entire foreign-born population in the Current Population Survey. See Figure 3, page 4, in their March 2006 estimate of the illegal population, http://pewhispanic.org/files/reports/61.pdf. Pew bases its 5.2 percent estimate on work done by Passel, Van Hook, and Bean. Their paper is entitled “Narrative Profile with Adjoining Tables of Unauthorized Migrants and Other Immigrants, Based on Census 2000: Characteristics and Methods,” which was produced for Sabre Systems as part of a contract with the Census Bureau. The undercount adjustment for illegal immigrants in particular is about 10 percent in Pew’s research. The Department of Homeland Security also assumes a 10 percent undercount in Census Bureau data, though DHS estimates are based on the American Community Survey (ACS), which is also collected by the Census Bureau. See page 3 of the DHS estimates in “Estimates of the Unauthorized Immigrant Population Residing in the United States: January 2006,” which can be found at http://www.dhs.gov/xlibrary/assets/statistics/publications/ill_pe_2006.pdf. The ACS and CPS are designed to produce similar estimates. It should be noted that the monthly files of the CPS used in this report do not include an over-sample of minorities as is the case with what is called the March supplement to the CPS. The March CPS is also referred to as the Annual Social and Economic Supplement. Pew’s estimate of the undercount is based on the March supplement and not just the “core” monthly file, used in this report. Typically, the March CPS produces estimates of the entire foreign-born population that are 1 percent larger than when just the core monthly CPS is used. This implies that the undercount of the illegal population in the monthly files used here is about 11 percent. It must be remembered that only an estimated 79 percent of the young, less-educated Hispanic immigrants shown in the figures are illegal aliens.

22 Those who take part in the CPS stay in the survey for several months, then leave for a time, returning again a few months later. This process creates a relationship with Census Bureau interviewers, which makes it less likely that interviewees would simply stop answering the Bureau’s questions all of a sudden. The Bureau also weights the data based on a complex methodology that reflects what the Bureau thinks is the nation’s actual population size by such key variables as race, sex, age, and ethnicity. The weighting procedure is specifically designed to produce accurate survey results even for populations that are difficult to capture in a survey. Weighting the data tends to smooth out sudden changes. Yet despite this fact, the figures show a sudden change in the number of less-educated, young foreign-born Hispanics in the United States.

23 The Department of Homeland Security estimates that 12 percent of the illegal population comes from Asia, and 4 percent comes from Europe.

24 If we assume that the illegal Hispanic population constitutes 80 percent of the illegal population and that it declined 11 percent, while the illegal non-Hispanic did not decline at all, then it would mean that the total illegal population fell 9 percent. On the other hand, not all of the young, less-educated Hispanic immigrants used in this study as a proxy for illegal aliens are in fact illegal aliens. It seems likely that if the 20 percent of the less-educated, young Hispanics who are legal immigrants were excluded, the drop in the illegal Hispanic population would be even steeper than the 11 percent estimated in this report. If we assume no drop in the young, less-educated legal Hispanic immigrant population, then the illegal component of this population would have to have declined 14 percent to produce the results in Figures 1, 2, and 4. Thus the possible range in the decline of the illegal population could be 9 to 14 percent, with 11 percent as the most likely middle range value.