A recent study from the Pew Hispanic Center indicates that net migration from Mexico has fallen to zero and may actually be negative. In other words, more people are leaving the United States and going to Mexico than are entering from our neighbor to the south. The data are somewhat difficult to obtain (since much of the immigration consists of undocumented persons), but if net migration is truly approaching zero or less, it's a major reversal of a long-standing pattern.

From the earliest records through about 1970, the Mexican-born population living in the United States was relatively small. However, the past 40 years have seen a sharp rise in inward migration and the number of Mexican-born persons living in the U.S. is currently estimated to be 12 million. Up to half of these immigrants may be unauthorized.

In a study released in February 2011, the Pew Hispanic Center noted a decline in the population of unauthorized immigrants (from a peak in 2007) stemming largely from a decrease in the number from Mexico. The same study also estimated the total number of unauthorized immigrants in the United States had tripled since 1990, when it was 3.5 million, and was up by a third since 2000.

California and Texas were found to have the largest populations of unauthorized persons, followed by Florida and New York. While the report indicated many states were experiencing declines in the numbers of undocumented residents, Texas was one area where they actually increased.

Several factors are likely contributing to the overall drop in net migration. First of all, the incentives to move to the United States have been greatly reduced by the weakened economy. (This also helps explain why Texas, where the economy has been relatively stronger, still seems to be experiencing an increase.)

Moreover, as reported in the Pew Hispanic Center study, the birth rate in Mexico has dropped substantially, from about 7.3 in 1960 to 2.4 in 2009. Slower population growth, particularly in younger age groups, works to shrink the Mexican workforce. As a result, there are fewer people vying for available jobs and, over time, fewer unemployed leaving the country to seek work in the United States. Moreover, Mexico saw a more rapid comeback from the global recession than the U.S., thus further enhancing relative opportunities.

Illegal crossings are also more difficult and dangerous due to increased enforcement as well as border violence. The consequences of being caught undocumented are higher, including deportation and/or a lower probability of ever being able to be naturalized. In 2010, some 282,000 unauthorized Mexican immigrants were repatriated by U.S. authorities. A growing number of these persons are indicating that they will not return.

It is somewhat ironic that the Supreme Court currently is hearing a challenge to Arizona's immigration law even as old patterns are reversed. Since its passage in 2010, Arizona's Senate Bill 1070 has generated heated debate and emotional response. Some characterize it as no more than a restating of federal law, but others see it as a dangerous move toward racial profiling and harassment of persons who are legally in the state. Governor Jan Brewer pointed to the high cost of dealing with illegal immigration ($1.6 billion per year for health care, incarceration, and education), although numerous studies (including a major one by The Perryman Group) point to a sizable net gain in economic activity and fiscal revenue.

Patterns in illegal immigration tend to track those in legal immigration, driven by factors such as the relative economic health of Mexico compared to the United States. Immigrants, both legal and illegal, serve as an important component of the U.S. workforce, especially in certain industries and geographic areas, and we need to be fully aware of that in the path we take toward immigration reform.

Net migration at or near zero may be due in part to tougher immigration policies and conditions, but I tend to think it's due more to changes in the relative opportunities for work here and in Mexico. We'd certainly like to see the pace of U.S. hiring at all levels increase, but I have no doubt that many Mexicans moving to America for work would far prefer a job in their own country. On the other hand, the ebb and flow across our Southern border primarily reflects the machinations of a labor market. Under normal conditions, the U.S. workforce cannot meet the demand for workers in certain occupational categories, and economic signals tend to bring people to jobs irrespective of politics or laws. As the national economy becomes more robust, this pattern will likely resume.

