New institutionalism has emerged as one of the most prominent research agendas in the field of comparative politics, Political economy, and public policy. This article examines the role of institutional variation in political/economic regimes in shaping tax burdens in industrialized democracies. An institutionalist model for tax policy variation is tested across the Organization for Economic Cooperation and Development (OECD) democracies. Countries are conceptualized and statistically modeled in terms of majoritarian, shifting coalition, and dominant coalition governments. Regression analysis and cluster analysis are used to statistically model cross-national tax burdens relative to the strength of labor organization and party dominance in parliament. This study finds that political and economic institutions are important in explaining tax policy variation. Specifying the structure of political and economic institutions helps to explain the size of the state in modern capitalist democracies. This article specifies and demonstrates which institutions matter and how much they matter