Behind the Pew Study on Illegal Immigration, Part IV: The Mystery of the Missing 900,000 Illegal Immigrants

At the heart of the Pew report is the finding that the overall estimated numbers of illegal immigrants in the United States have declined from a peak of 12 million to 11.1 million, a net decline of 900,000 illegal immigrants. At least, this is what the report's title suggests that Pew believes is its most noteworthy finding. The decline is also the point that almost all accounts of the Pew report emphasize.

In this entry, I would like to "stipulate" the general accuracy for the report's numbers (which are, after all, close to CIS's own estimates from July of last year), even though obvious questions could be asked regarding their accuracy for the purpose of further inquiring into a very basic question: Where did those 900,000 illegal immigrants actually go?

What the report says about this has been largely overlooked. Missed in all the excitement about the decline in numbers was the wording of the report: "the annual inflow of unauthorized immigrants to the United States was nearly two-thirds smaller in the March 2007 to March 2009 period than it had been from March 2000 to March 2005" (p. i, emphasis added). To repeat, that is a decline in the number of people arriving. It does not represent a surge or even in the uptick of illegal immigrants heading home.

Here is how the Pew study phrases it: "during the first half of the decade, an average of about 850,000 new unauthorized immigrants entered each year, increasing the unauthorized population from 8.4 million in 2000 to 11.1 million in 2005. Since then, the annual inflow has dropped to about 550,000 per year from March 2005 to March 2007, and declined further to an average of 300,000 per year for March 2007 to March 2009. As a result, the unauthorized population in 2009 returned to the level it had been in 2005” (p. iii, emphasis added). That would be 900,000 fewer illegal immigrants living in the United States.

The use of the words "as a result" implies that it is the slowing of the flow into the United States that has caused the decline of the illegal immigrant population living in the United States.

But how did this happen? Does a reduced flow of illegal immigrants into the country reduce the numbers of those already in the country? Only if 900,000 illegal immigrants, the difference between the estimate illegal population living in the United States in 2007 and in 2009 have either died or left the country or were legalized, and there doesn't seem to be evidence for any of these occurring.

The Pew study explicitly says that, "the most marked decline in the population of unauthorized immigrants has been among those who come from Latin American countries other than Mexico." The Pew report then says, "Even though the size of the Mexican unauthorized population living in the United States has not changed significantly since 2007, the inflows from that country have fallen off sharply in recent years" (pp. i-ii, emphasis added). Correspondingly, "the Mexican unauthorized population (which accounts for about 60% of all unauthorized immigrants) peaked in 2007 at 7 million and has since leveled off" (p. i). Moreover, there is, "no evidence of a recent increase in the number of Mexican- born migrants returning home from the U.S." (p, iii).

There has apparently been no decline in visa overstayers either. In a 2006 study, the Pew Hispanic Center estimated that almost half of the then estimated 11.5-12 million illegal immigrants in the U.S. came here with visas and stayed after they expired. At a congressional hearing on the subject, a news account reports that a top official with Immigration and Customs Enforcement testified that, "Since 2007, more than 300,000 individuals each year have remained after their visas expire." That number would translate to more than a million new illegal immigrants every four years. These of course are estimates since, as noted, the United States does not have a system in place that would allow officials to check exits against entries. (See here for a report on a recent CIS symposium on this issue of tracking exits.)

The Pew study specifically notes that, "The number of unauthorized immigrants from the rest of the world did not change" (p.i, emphasis added).

As noted above, the Pew report "finds that the most marked decline in the population of unauthorized immigrants has been from those Latin American countries other than Mexico" (p. i). Where are these illegal immigrants? The best the report can manage on this is the very tepid, "However, return flows to other countries may have increased" (p. iii, emphasis added). However, since absolutely no records are kept on those who leave the country, whether they walk back across our borders or leave at the end of their visa stays (or don't), it is impossible to say.

Moreover, the declines have been "especially notable along the nation's Southeast coast and in its Mountain West" (p. ii). Surely an exodus of almost a million people, many if not most of them from two small groups of states, within the relatively short period covered by report, would have made some discernable impact on the communities they left, caused an uptick in airline reservations heading south, border crossing statistics, or other indicators. However, little mention of these metrics has surfaced.

So while the number of new illegal immigrants entering the United States from Latin American countries other than Mexico, which is the source of the largest group of illegal immigrants living in the United States, has declined, the number of visa overstayers and illegal immigrants from other parts of the world "did not change." And there is little if any evidence of a massive exodus of illegal immigrants back to their countries of origin. Yet Pew reports a very large and significant decline in the (estimated) number of illegal immigrants living in the United States.

Quite the mystery.