Determinants of Illegal Mexican Immigration into the US Southern Border States

We model illegal immigration across the US-Mexico border into Arizona, California, and Texas as an unobservable variable applying a Multiple Indicators Multiple Causes model. Using state-level data from 1985 to 2004, we test the incentives and deterrents influencing illegal immigration. Better labor market conditions in a US state and worse in Mexico encourage illegal immigration while more intense border enforcement deters it. Estimating the state-specific inflow of illegal Mexican immigrants we find that the 1994/95 peso crisis in Mexico led to significant increases in illegal immigration. US border enforcement policies in the 1990s provided temporary relief while post-9/11 re-enforcement has reduced illegal immigration.