Inequality and conflict are inextricably linked. A considerable amount of research has been done attempting to understand the links between the two. Both vertical (between households or individuals) and horizontal inequality (between groups) as well as perceived inequality have been examined. In this report, we review and synthesize the large literature on inequality and conflict and perform a mapping exercise for data on vertical, horizontal, and perceived inequality. We show that while vertical (economic) inequality is at an all-time high, horizontal inequality has declined steadily throughout the world over the past 25-30 years. Indeed, in sharp contrast to vertical inequality, horizontal inequality is at the lowest levels on record.