It is appropriate to take stock of extant measures of income inequality as they pertain to their utility in cross-national models of political and economic performance. Are some measures more reliable and valid than others? What about data coverage, conceptual mapping of similar indicators, functional form specification matters? This paper specifies models of cross-national democratic and economic performance, with common, industry-standard variables such as economic growth and development level, globalization, political culture (colonialism, ethnicity, religion), and economic type (world-system), and insert various measures of income inequality (Hoover, Deininger and Squire, Galbraith, and UNU-WIDER). The intent is to compare and contrast model robustness under conditions of variable country coverage, inequality definitions, and measurement strategies. With both practical and conceptual matters in mind, the hope is to become better acquainted with the consequences of variable choice in income inequality data usage and modeling techniques.