The major crime-reduction strategy in this country is to imprison more and more criminals. Past studies of its effectiveness in reducing homicide have produced wildly divergent results. The authors analyze the homicide-prison relationship with a time series over 1930-1994, finding that a 10% increase in prison population is associated with roughly 13% fewer homicides. The authors also studied assault and robbery, two crime types linked to homicide, and again found negative associations with prison population.