"The relationship between economic and political inequality has long concerned social scientists, but research remains limited in scope. Most studies focus on isolated cases, highly restricted subsamples, or subunits within countries. Using data for up to 136 countries between 1981 and 2011, this study analyzes whether and how income inequality affects the distribution of political power for, and respect for the civil liberties of, a society's rich and poor people. When income inequality is high, do rich people command greater political power and enjoy stronger civil liberties than poor people do? To answer these questions, the study uses both pooled regression analyses and two-stage models with instrumental variables to identify causal effects. The results are decisive: income inequality is inimical to both political and civil equality. These findings hold for developed as well as developing countries and for democratic as well as nondemocratic countries."

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