Civilian Mass Killings Perpetrated by Nonstate Actors: Data Trends and Theoretical and Empirical Risk Factors

Abstract This article addresses two research questions: (1) What are recent trends in nonstate actor (NSA) civilian mass killings by country locations and perpetrator groups? and (2) What are risk factors for NSA civilian mass killings based on economic choice theory and large-sample empirical inquiry? We summarize recent data on mass killings perpetrated by various NSAs including rebel groups; political, territorial, and identity militias; and terrorist organizations. Following a review of the empirical NSA mass killing literature, we develop an economic choice model of a NSA’s resource allocations to direct (military) fighting and to violence against civilians when in contestation with a government over political, territorial, and/or ideological (identity) control. Our literature review and theoretical model guide our empirical inquiry into risk factors for NSA mass killings for a sample of 199 countries from 1989 to 2023. We find that low economic development, anocracy, natural resource dependency; high young male unemployment; ethnic division; population; civil and nonstate wars; regime change; and government mass killings each significantly elevate NSA mass killing risk. We conclude with suggestions on how NSA mass killings might be prevented or at least made less severe.