Facts or Ideology: What Determines the Results of Econometric Estimates of the Deterrent Effect of the Death Penalty? A Meta-Analysis

Given that as a whole the literature on the deterrent effect of capital punishment is inconclusive, the fact that individual authors persistently claim to have found solid evidence in one or the other direction raises two questions. Firstly, what are the causes of these different results? Do different data samples, estimation methods or time periods lead to different results or do the outcomes merely reflect prior convictions on the part of the authors? Secondly, to what extent is it possible to derive such divergent results by slightly changing the specification of the test equations without violating scientific standards? After conducting a survey of the more than forty available reviews of this literature, we present a meta-analysis of 102 deterrence studies published between 1975 and 2011. The only statistically significant explanatory variable in these studies turned out to be the profession of the author: Economists claimed significantly more often than members of legal or other social science departments to have found a significant deterrent effect. Furthermore, using a panel data set of U.S. states, we show how easy it is to derive contradictory results by employing alternative specifications. Thus, our results reinforce the claim that the empirical evidence presented to date is far too fragile to provide a basis for political decisions.