"In the 1990s, while there was a large decline in property-related crime along the U.S.-Mexico border, violent crime rates began to converge to the national average. At the same time, legal and illegal immigration from Mexico surged and border enforcement rose to unprecedented levels. In this paper, we investigate the relationship between border county crime rates, immigration and enforcement since the early 1990s. We find that while the volume of illegal immigration is not related to changes in property-related crime, there is a significant positive correlation with the incidence of violent crime. This is most likely due to extensive smuggling activity along the border. Border enforcement meanwhile is significantly negatively related to crime rates. The bad news is that the deterrent effect of the border patrol diminishes over this time period, and the net impact of more enforcement on border crime since the late 1990s is zero"--Federal Reserve Bank of Dallas web site.