In the study of civil conflict, many regard ethnic fractionalization as a measure of grievance. However, there is also a rational-actor explanation as to why ethnicity might cause rebellion. A third possibility is that ethnic fractionalization in itself causes civil war. Using a novel approach, we provide an empirically based answer to the question of which of these 3 mechanisms is most prominently at play. First, we present our updated index of ethnolinguistic fractionalization. We have recalculated the index so that it corresponds with today’s ethnic compositions, using interpolation to fill in values between 1990 (the last recordings of the old measure) and our own data from 2011. Second, we establish empirically that there is indeed a positive (though slightly curvilinear) link between ethnicity and civil conflict. Third, we present 2 factor analyses, both of which demonstrate that ethnicity in itself is a mechanism that explains the outbreak of civil conflict
