America's Soaring Prison Population.

Factors widely reported to explain record prison population increases since 1973 were generally not substantiated in national data. No clear evidence was found that prosecutors were increasingly using mandatory prison sentencing laws, that judges were imposing longer prison sentences than previously, or that parole boards were making prisoners serve longer before their first release. Changes since 1973 in population demographics and in police-recorded crime and arrest rates were found to have only a modest impact on prison population growth. The war on drugs was found to have only a small impact despite increased drug arrest and imprisonment rates. One change found to have a major impact was the increased chance of a prison sentence after arrest for nearly every type of crime. This change has helped to drive incarceration rates to their highest levels ever. Accompanying rising incarceration rates have been gradual reductions in U.S. crime rates after 1973, according to annual crime victimization surveys. The possibility that rising incarceration rates are helping to reduce crime must be weighed in debates about America's prisons.