Tighter enforcement along the US-Mexico border backfired, researchers find

"Rather than stopping undocumented Mexicans from coming to the U.S., greater enforcement stopped them from going home," said Douglas Massey, one of the researchers and the Henry G. Bryant Professor of Sociology and Public Affairs at Princeton.

Advocated by bureaucrats, politicians and pundits, the militarization of the U.S. border with Mexico transformed undocumented Mexican migration from a circular flow of predominantly male workers going to a few states into a settled population of about 11 million in all 50 states, Massey said. From 1986 to 2010, the United States spent $35 billion on border enforcement and the net rate of undocumented population growth doubled, he said.

"By the 1990s border enforcement had become a self-sustaining cycle in which rising apprehensions provided proof of the ongoing 'illegal invasion' to justify more resources allocated to border enforcement, which produced more apprehensions, even though the actual number of undocumented migrants seeking entry was not increasing," Massey said.

The research is detailed in an article, "Why Border Enforcement Backfired," that was published by the American Journal of Sociology in March. The authors are Massey, Jorge Durand of the Centro de Investigación y Docencia Económica in Mexico City and Karen Pren, project manager of the Mexican Migration Project at Princeton's Office of Population Research.

The research was supported by funding from the National Institute of Child Health and Human Development as well as the John D. and Catherine T. MacArthur Foundation.

While advocates of increased border enforcement argued it would slow undocumented immigration, Massey said data gathered from communities throughout Mexico since 1987 on histories of migration and border crossings point to the opposite effect.

"Greater enforcement raised the costs of undocumented border crossing, which required undocumented migrants to stay longer in the U.S. to make a trip profitable," he said. "Greater enforcement also increased the risk of death and injury during border crossing. As the costs and risks rose, migrants naturally minimized border crossing -- not by remaining in Mexico but by staying in the United States."

The authors say this is a good time to shift from a policy of immigration suppression to one of immigration management.

"Mass immigration from Mexico has ended and won't be coming back owing to the decline of Mexican fertility from 6.5 children per woman in the 1960s to around 2.2 children per woman today, roughly replacement level," Massey said. "Labor force growth in Mexico has dropped sharply and Mexico is now becoming an aging society in which fewer and fewer people are in the migration-prone ages of 15-30, so the pressure is off in a demographic sense."

Most migration now is legal, Massey said, a situation that will continue so long as temporary work visas are matched with U.S. labor needs.

"The greatest need now is a path to legal status for the 11 million undocumented residents who are already here, who mostly have been here now for 15 years or more and increasingly have U.S. citizen children," he said. "If we were to grant these people permanent legal status, many would actually return home, secure in the knowledge they could re-enter whenever they want."

Mary Waters, the M.E. Zukerman Professor of Sociology at Harvard University who studies immigration, said the research highlights the folly and waste of American immigration policy.

"This is a very important article that looks at a long sweep of history and provides the very best data and analysis to lead to a conclusion that most Americans would find very counter-intuitive," said Waters, who wasn't involved in the research. "Throwing money at militarizing the border led to the growth of undocumented immigration and if we had just done nothing, undocumented immigration would be much lower."

Waters said policymakers should pay attention to this research.

"This is social science research at its very best -- addressing an important public policy question with state of the art methods and painstakingly collected empirical data," Waters said.