A study by Fish et al (2010) concludes:
Relying on cross-national analysis, the authors find no evidence of a
correlation between the proportion of a country’s population that is
made up of Muslims and deaths in episodes of large-scale political
violence in the postwar period.
- Data is from 1946-2007, so is comprehensive, but over 10 years old now.
- Only considers "large-scale acts of domestic political violence" (ie, YMMV).
- Just one study, though the author does have a book out (2011) reviewing more research on the subject.
On the other hand, it looks at both total number of acts and people killed, predominantly Muslim countries vs proportion of Muslims in countries, attempts to control for socioeconomic factors, outliers, ambiguity in the data, and other factors. Using a variety of different models and criteria to see if any of them affect results, the conclusions are pretty much the same.