More violence

After I blogged Cirillo and Taleb’s new paper on the long-term trend in war deaths, I read other commentaries on the debate (William Briggs, Dart-Throwing Chimp, STATS.org) and interacted with the authors. All that sharpened my thinking. Refinements: The paper is postured as a rejoinder to Steven Pinker. But I think if you are going use statistics to show that someone else is wrong, you should 1) state precisely what view you question, 2) provide examples of your opponent espousing this view, and 3) run statistical tests specified to test this view. Cirillo and Taleb skip the first two and hardly do the third. The “long peace” hypothesis is never precisely defined; Pinker’s work appears only in some orphan footnotes; the clear meaning of the “long peace”—a break with the past in 1945—is never directly tested for. Largely, the paper argues that the historical data do not appear improbable if we assume no trend over 2,000 years in war deaths. That is, the data are consistent with no trend. Pinker argues that the data are compatible with a decline, at least after 1945. But the first statement does not contradict the second. Normally competition between models is decided by fitting a single model that encompasses both, then testing whether a differentiating parameter, such as the coefficient on a post-1945 dummy, is statistically different from zero. As I explained last time, Cirillo and Taleb could do that with their models but don’t. So there is hardly any direct confrontation of the two theories. The cause for the modifier “hardly” is a single graph in the paper, Figure 8. Cirillo and Taleb check whether the average number of years between significant wars (those causing at least 50,000 deaths...