with Aaron Chalfin
A large literature establishes that hiring police officers leads to reductions in crime and that investments in police are a relatively efficient means of crime control compared to investments in prisons. One concern, however, is that because police officers make arrests in the course of their duties, police hiring, while relatively efficient, is an inevitable driver of "mass incarceration." This research considers the dynamics through which police hiring affects downstream incarceration rates. Using state-level panel data as well county-level data from California, we uncover novel evidence in favor of a potentially unexpected and yet entirely intuitive result --- that investments in law enforcement are unlikely to markedly increase state prison populations and may even lead to a modest decrease in the number of state prisoners. As such, investments in police may, in fact, yield a "double dividend'' to society, by reducing incarceration rates as well as crime rates.