We study the migration policy set by a welfare maximizing government in a model where immigrant workers differ in their skills and are imperfectly matched with heterogenous occupations. The policy fixes a minimum skill level for legal migrants, and foreign workers that fall below it can only...

In 2008, approximately 12 million immigrants lived illegally in the United States, and large numbers of undocumented foreigners resided also in other advanced destination countries. Hence, attempts at controlling immigration flows seem to often fail. If governments are not enforcing their...