Introduction: Inequality is one of the most pressing social issues of our time, yet individuals often differ in how they perceive and evaluate it. These subjective differences hinder the formation of a common understanding, making it difficult to reach consensus on how to address inequality. This research investigates the role of fairness beliefs-specifically just world beliefs (BJW) and meritocracy-in shaping individual perceptions of inequality. Methods: We conducted three studies across four independent samples (Ns between 543 and 36,281), using experimental, survey, and cross-national designs. Study 1 experimentally manipulated fairness beliefs. Study 2 analyzed two representative German samples. Study 3 employed multilevel modeling with data from 40 countries. Results: Fairness beliefs, particularly belief in a just world (BJW), consistently influenced both the perceived and evaluated size of financial inequality across all three studies. Experimental evidence (Study 1) showed a causal effect of BJW on both these components. In large-scale observational data (Studies 2 and 3), BJW remained a significant predictor of perceived and evaluated inequality across diverse national samples. Discussion: These findings suggest that BJW not only influences how people evaluate inequality but also shapes their perception of its scale. By identifying fairness beliefs as a core factor behind subjective inequality, this work provides insights into the psychological roots of disagreement about inequality and offers a foundation for addressing these divides in public discourse and policy.
