MIGRANT COHORT SIZE, ENFORCEMENT EFFORT, AND THE APPREHENSION OF UNDOCUMENTED ALIENS

This article examines macro-structural conditions that affect time tre nds in aggregate probabilities of undocumented alien apprehension alon g the Mexico-US border. We show that the number of migrants attempting to cross the border illegally in a given period and the level of effo rt expended by the INS to apprehend undocumented migrants are principa l determinants of apprehension probabilities. Our findings differ from those in earlier work by Donate, Durand, and Massey who argue that in dividual, household, and community factors are not significant predict ors of apprehension probabilities and conclude that escaping INS detec tion at the border is essentially a random process unrelated to person al traits or to enforcement provisions of the 1986 Immigration Reform and Control Act. Although Donate et al. recognize that apprehension pr obabilities are affected by the size of the US Border Patrol budget an d the number of personnel, they omit these larger structural factors f rom consideration. Instead, they introduce annual dummy variables to c ontrol for macro-structural forces. This approach is unsatisfactory be cause it confounds the effects of numerous explanatory factors. We con clude that one implication for future research is that it is worth mod eling the effects of individuals' characteristics on apprehension prob abilities by including as predictors an estimate of the flow of undocu mented migrants and measures of INS border enforcement effort. Control ling explicitly for three macrostructural conditions may disclose the importance of some individual-level factors that would otherwise be ob scured.