“[O]ur recent research shows that each execution carried out is correlated with about 74 fewer murders the following year… The study examined the relationship between the number of executions and the number of murders in the U.S. for the 26-year period from 1979 to 2004, using data from publicly available FBI sources… There seems to be an obvious negative correlation in that when executions increase, murders decrease, and when executions decrease, murders increase…

In the early 1980s, the return of the death penalty was associated with a drop in the number of murders. In the mid-to-late 1980s, when the number of executions stabilized at about 20 per year, the number of murders increased. Throughout the 1990s, our society increased the number of executions, and the number of murders plummeted. Since 2001, there has been a decline in executions and an increase in murders.

It is possible that this correlated relationship could be mere coincidence, so we did a regression analysis on the 26-year relationship. The association was significant at the .00005 level, which meant the odds against the pattern being simply a random happening are about 18,000 to one. Further analysis revealed that each execution seems to be associated with 71 fewer murders in the year the execution took place…

We know that, for whatever reason, there is a simple but dramatic relationship between the number of executions carried out and a corresponding reduction in the number of murders.”