Continuing my focus on cross-national homicide, I correlated rates with the percent of the population that is Muslim. For a sample of 181 countries, the correlation is -.17 which means that countries with more Muslims tend to have less murder. This is striking when one considers that Muslim-dominated countries tend to be poor and some of them are sub-Saharan African. After adjusting for per capita GDP and percent black, the correlation is likely to be stronger.
One note: I'm going to try to get a better idea of how relilable the homicide data are. I chose coroner's data over criminal justice data simply because I trust public health institutions more, and they tend to report more counts of homicide (suggesting that criminal justice agencies are not reporting some cases). The two systems seem to be pretty consistent in high-income countries, but just eyeballing the data, the counts from the two sources can be very different in poor countries. I suspect that politically-motivated killings in unstable countries complicate things.