Very Impressive Evidence that More Incarceration Implies fewer Homicides
From Bernard Harcourt
The key idea which was new to me was summing the prison and the mental hospital population. Then the recent huge increase in the prison population just cancels the earlier huge decline in the mental hospital population and the sum mirrors the homicide rate.
The pattern holds up in a state level panel with state effects and time effect.
Harcourt does not look at causation, but the simultaneity bias should go the other way (high crime causes high incarceration).
Kargan take notice