02/19/2013 02:48 pm ET | Updated Apr 21, 2013

Immigration Policy and New Estimates of the U.S. Unauthorized Population

A recently released report on the U.S. unauthorized population comes at a politically charged moment, as Congress begins in earnest to consider immigration reform and a possible path to citizenship for the nation's unauthorized residents. The report, co-authored by Robert Warren, former demographer of the U.S. Immigration and Naturalization Service, and John Robert Warren, professor of sociology at the University of Minnesota, puts the size of the unauthorized population at 11.7 million as of January 2010. The report's findings are highly relevant to the U.S. immigration debate.

First, the report documents modest success in meeting a goal shared by partisans on both sides of the immigration divide; i.e., reducing the unauthorized population. It finds that unauthorized "arrivals" or "inflows" declined in every state but Mississippi (and Washington, D.C.) between 2000 and 2009. Over the same period, "departures" or "outflows" from this population increased in every state. In some states, unauthorized arrivals continued to outpace departures. However, the number of unauthorized residents fell in 29 states and Washington, D.C. during this period. Moreover, unauthorized arrivals plummeted nationally from 1.39 million to 384,000 over the same period, while departures rose from 369,000 to 558,000. As a result of these trends, the U.S. unauthorized population decreased in 2008 and 2009.

Second, the report highlights the dynamism of the unauthorized population and, in particular, the role of "departures" in shaping this population. It shows that the largest single cause of "departures" is not formal removals (deportations), but emigration. Moreover, it concludes that emigration of the unauthorized did not increase in 2008 and 2009, despite the Great Recession and record levels of immigration enforcement. In addition, it finds that nearly 5.7 million U.S. unauthorized residents had entered prior to 2000 as of January 2010. Of course, the longer an immigrant remains, the greater the likelihood that he or she will seek to remain permanently: in fact, the report assumes a decline in emigration rates for the unauthorized over time.

The existence of an entrenched unauthorized population of this magnitude suggests the need for more than status quo, enforcement-only policies. An effective response to this challenge requires extending legal status to a large percentage of unauthorized, particularly long-term residents. The report's findings might be seen to complement a growing body of research which demonstrates that strict border enforcement policies have led unauthorized laborers - who might otherwise have come and gone as their work demanded -- to stay in the United States for longer periods and has, thus, incentivized illegal migration by their families as well. Both sets of research suggest the need for immigration policy reforms that combine enforcement, with new avenues to legal status.

Third, the report finds that nearly two-thirds of U.S. unauthorized residents live in California, Texas, Florida, New York, Illinois, New Jersey and Georgia. Yet, of these states, only Georgia is among the seven states with the fastest growing unauthorized populations. Between 1990 and 2010, Alabama, South Carolina, North Carolina, Tennessee, Arkansas, Kentucky, and Georgia each experienced more than an eleven-fold increase in their unauthorized populations. Perhaps not coincidentally, these states have been flashpoints for anti-immigrant anger and activism. Three of them - Alabama, South Carolina and Georgia - passed omnibus immigration enforcement laws. It may well be that the rate of growth of the unauthorized population contributes more to social discord over immigration than does the overall number of unauthorized residents.

The report relies on the "residual method" to arrive at its unauthorized estimates. This method compares the total foreign-born population using Census data (with undercount assumptions), to the total number of authorized immigrants based on federal administrative data, to yield (residual) estimates of the unauthorized. The report provides state by state estimates for each year from 1990 to 2010 of unauthorized inflows through illegal entry and visa overstays, as well as outflows from this population through emigration, removal, graduation to legal status, and death. It combines state figures to arrive at its national estimates. The report admittedly excludes certain categories of legal immigrants from its count of authorized immigrants, thus slightly overestimating the number of unauthorized immigrants. It also seems to assume that all "removed" immigrants lack legal status, although lawful permanent residents are also subject to removal. Most importantly, however, it provides a strong factual baseline for policymakers and planners at a time of intensifying debate and anticipation of immigration reform.