This dissertation argues that public opinion regarding the acceptability and desirability of income differences is affected by actual income inequality. Cross-national survey evidence is combined with laboratory and survey experiments to show that estimates regarding appropriate income differences depend on (perceptions of) real income differences. When income inequality changes, public opinion "habituates" by adjusting expectations for fair levels of inequality in the same direction as the factual change. The adjustment occurs because humans are subject to status quo bias and have a motivated tendency to believe in a just world. In the context of increasing inequality in developed democracies over the last 40 years, the implication is that...