ABSTRACT
This chapter describes the principal results of studies using these two approaches and uses these results to estimate the extent to which the prison buildup is responsible for the recent crime reductions. It examines the principal threats to validity and limitations on each study’s applicability. Although one cannot be certain as to the role of prison expansion, one can use the available information to develop a reasonable estimate. The effectiveness of prisons at controlling crime has been an important research issue since at least the late 1960s, when the current prison boom began. The most likely explanation for the much higher national-level elasticities is that the national prison population is a proxy for one or more as-yet unmeasured variables. Levitt’s model is the only one to account explicitly for the possibility that, just as prison population influences the crime rate, so can crime rates influence the prison population.
