When and why ethnic groups rebel remains a central puzzle in the civil war
literature. In this paper, we examine how different types of inequalities
affect both an ethnic group’s willingness and opportunity to fight. We argue
that political and economic inter-group inequalities motivate ethnic groups
to initiate a fight against the state, and that intra-group economic
inequality lowers their elite’s costs of providing the necessary material
and/or purposive incentives to overcome collective action problems inherent
to rebel recruitment. We therefore predict that internally unequal ethnic
groups excluded from power and/or significantly richer or poorer relative to
the country’s average are most likely to engage in a civil war. To assess
our claim empirically, we develop a new global measure of economic
inequality by combining high-resolution satellite images of light emissions,
spatial population data, and geocoded ethnic settlement areas. After
validating our measure at the country- and group level, we include it in a
standard statistical model of civil war onset and find considerable support
for our theoretical prediction: greater economic inequality within an ethnic
group significantly increases the risk of conflict, especially if political
or economic inequalities between groups provide a motive.