The Imprisonment Binge and Crime
THIS CHAPTER EXAMINES the association between crime and imprisonment in the United States since 1973. One of the interesting features of this period was that the number of people imprisoned and the rate of imprisonment both showed a persistent annual increase. This circumstance establishes conditions required for a [natural] experiment assessing the impact of imprisonment on crime to the extent that one of the key elements, incarceration, was constantly increased. Following the logic of both the deterrence and incapacitation approaches, there should be a persistent decrease in crime, if incarceration is an effective crime control strategy and no other factors affect the level of crime in society. Here, it is not necessary to determine whether it is incapacitation or deterrence that affects crime. Rather, the concern is whether an increase in incarceration produces the desired result—a decline in crime. A number of different strategies were employed to address this issue.
One way to assess the association between imprisonment and crime is to calculate change ratios. Change ratios can be employed to determine the relationship between changes in crime and imprisonment.
The numerator in the change ratio calculated here is the percent change in the number of index crimes (those crimes that make up the Federal Bureau of Investigation's [crimes index]: murder, rape, robbery, assault, larceny-theft, motor vehicle theft, burglary, and arson) known to police per 100,000 citizens. The denominator in the change ratio will be the lagged percent change in the number of inmates in prison.1 The denominator is lagged one year on the assumption that the deterrent or incapacitative effect of incarceration does not have an immediate effect on crime, but rather a future impact on offending. While a one-year lag may