Has the U.S. Prison Boom Changed the Age Distribution of the Prison Population?

Shawn Bushway, University at Albany, State University of New York (SUNY)
Hui-shien Tsao, University at Albany, State University of New York (SUNY)
Herbert L. Smith, University of Pennsylvania

This paper provides a detailed exposition of changes in the age-incarceration distribution during the period of mass incarceration. We first provide an extensive ‘proof’ of the inmate surveys in the U.S. state prisons. We document that the prison population expanded and the age distribution shifted dramatically to the right. An age-period-cohort model is estimated to determine to what extent the observed changes in the distribution could be explained by changes in how birth cohorts are treated by the criminal justice system. We found that cohort effects could explain the observed shifts in the prison population extremely well. The younger cohorts from the 1970’s and 1980’s appear to have more people incarcerated than did the older cohorts from the same period. The most plausible explanation is that there are simply more people in these cohorts. However, after controlling for the size of the population, we found essentially the same result.