Column 3 in table 1 may provide some evidence. The numbers reveal several things. First, of the countries that have declining crime rates over the 1988-98 period, all but Denmark show an increase in incarceration over the same decade. The UK does not fit this exact pattern, but it has seen a very sharp decline in crime since 1991, and also has had, as column 3 shows, one of the larger increases in the rate of incarceration. But the table reveals many anomalies with this analysis as well.
Several countries have higher rates of incarceration and higher crime rates.
Clearly, a more subtle assessment is required for a complete explanation for the changing pattern of crime. To get a clear answer, we need to account for crime rates that measure different things in different countries, and rates of incarceration that are also measured differently across countries. Once we make these adjustments, an association emerges between the changes in the crime rate and changes in the incarceration rate. In fact, preliminary statistical evidence suggests that a 10 percentage point change in the incarceration rate leads to a 7.5 percentage point reduction in the crime rate. Although there is much more to say about this issue, it is interesting that the international data tend to support the negative effect of incarceration on the crime rate.