Over the past twenty-five years, the U.S prison system has experienced continuous substantial increment in the prison population. At the same time, incarceration rates have risen by more than 300%, a phenomenon that many analysts have referred to as mass incarceration (DeFina & Hannon, 2013)....

This paper investigates the influence of friends on crime, using data I collected among the homeless. To estimate the causal effects of friends and of the share of criminal friends on crime, I rely on two instruments. The first is the share of rainy days during one's first year as homeless:...