The Effect of Social Connectedness on Crime: Evidence from the Great Migration
利用1970-2009年美国城市数据，发现非裔美国人从南方迁移时形成的同乡网络（社会联系）显著降低了谋杀、抢劫等犯罪，社会联系每增加一个标准差，谋杀率下降21%。
Abstract This paper estimates the effect of social connectedness on crime across U.S. cities from 1970 to 2009. Migration networks among African Americans from the South generated variation across destinations in the concentration of migrants from the same birth town. Using this novel source of variation, we find that social connectedness considerably reduces murders, rapes, robberies, assaults, burglaries, and motor vehicle thefts, with a 1 standard deviation increase in social connectedness reducing murders by 21% and motor vehicle thefts by 20%. Social connectedness especially reduces murders of adolescents and young adults committed during gang and drug activity.