Estimates of the Deterrent Effect of Capital Punishment: The Importance of the Researcher's Prior Beliefs

Abstract

Researchers from different social sciences approach the issue of the deterrent effects of capital and noncapital punishments with conflicting prior beliefs. Some believe that punishments deter and that social and economic variables have little or no influence on the murder rate. Others believe that punishments have little or no impact and that variations in the murder rate between states (or over time) can be explained largely by variations in economic and social conditions. Others hold somewhat different views. If controlled experiments could be designed to test the competing hypotheses, researchers could assess their validity. However, since research in the effectiveness of punishments in reducing the murder rate must be carried out in a nonexperimental setting, there is much uncertainty as to the "correct" empirical model that should be used to draw inferences, and each researcher typically tries dozens, perhaps hundreds, of specifications before selecting one or a few to report. Usually, and understandably, the ones selected for publication are those that make the strongest case for the researcher's prior hypothesis. Because of this,