Change point analysis of historical battle deaths

Abstract

It has been claimed and disputed that World War II has been followed by a ‘long peace’: an unprecedented decline of war. We conduct a full change point analysis of well-documented, publicly available battle deaths data sets, using new techniques that enable the robust detection of changes in the statistical properties of such heavy-tailed data. We first test and calibrate these techniques. We then demonstrate the existence of changes, independent of data presentation, in the early to mid-19th century, as the Congress of Vienna system moved towards its collapse, in the early to mid-20th century, bracketing the World Wars, and in the late 20th century, as the world reconfigured around the end of the Cold War. Our analysis provides a methodology for future investigations and an empirical basis for political and historical discussions.