Illegal Immigration, Border Enforcement, and Relative Wages: Evidence from Apprehensions at the U.S.-Mexico Border

This paper examines the determinants of illegal immigration in the United States from Mexico from 1976 to 1995. The main challenge in the empirical work is that the observations are not the number of individuals that attempt to enter the United States illegally, but rather the number of individuals apprehended attempting to cross the U.S.-Mexico border illegally. Based on a simple model of the individual migration decision, we postulate the existence of an apprehensions function, which expresses the number of apprehensions at the U.S.-Mexico border as a function of the number of illegal attempts to cross the border an the level of border-enforcement effort exerted by the U.S. government.