The Long-Run Effect of Mexican Immigration on Crime in US Cities: Evidence from Variation in Mexican Fertility Rates

Using historical data on the size of state-specific Mexican birth cohorts and geographic migration networks between Mexican states and US metropolitan areas, I construct an instrumental variable that predicts decadal migration from Mexico to the United States. The intuition behind this identification strategy is that larger historical birth cohorts in Mexico yield more potential migrants once each birth cohort reaches prime migration age. I report evidence that Mexican immigration is associated with a decline in property crimes and an increase in aggravated assaults. The available evidence suggests that this is not an artifact of reduced crime reporting among immigrants.