Border Security and the "Cage" Effect

For a comprehensive overview of the number of undocumented aliens in the United States over the past quarter century, see the new Congressional Research Service report: Unauthorized Aliens Residing in the United States: Estimates Since 1986. The unauthorized alien population has climbed sharply over the years, from 3.2 million in 1986 to 11.2 million in 2010. One possible reason for the large increase, according to the report:

"Some researchers also suggest that the increased size of the unauthorized resident population during the late 1990s and early 2000s is an inadvertent consequence of border enforcement and immigration control policies. They posit that strengthened border security has curbed the fluid movement of seasonal workers. This interpretation, generally referred to as a caging effect, argues that these policies have raised the stakes in crossing the border illegally and created an incentive for those who succeed in entering the United States to stay."