The economic effects of policy options help explain why individuals support some reforms while they oppose others. However, disentangling the egoistic and sociotropic origins of voter preferences has proven difficult. We conduct an experiment that details how a reform affects one’s personal income, the average income in the country, and different income groups. The results suggest that the causal effect of personal income changes on reform support is about twice the size of changes in a country’s income average. Voters specifically care about how reforms impact the poor, and this prosocial concern depends neither on their own income level nor on how a policy will affect them personally. These patterns characterize how voters evaluate the redistributive effects of generic economic policies, health care reforms, trade-policy decisions, and the policy platforms of candidates running for office.