Party Systems and Country Governance focuses on party systems their variations across the world and their effects on country governance. It is also about the conceptualization and measurement of country governance. In the language of research, party system traits are the independent variables and country governance scores are the dependent variables. According to the normative values of democratic theory, the presence of competitive, aggregative, stable systems of political parties contributes to better country governance. International aid agencies have tended to accept the normative theory, assuming its truth. As a result, they have spent millions of dollars in efforts to develop competitive, aggregative, stable party systems. This study translates the normative theory into testable empirical theory. It provides evidence that largely, but not completely, supports the assumptions of aid agencies. The nature of a country's party system affects the quality of its governance. To measure governance, the authors used the existing World Bank Governance Indicators for 2007 on 212 countries. Using Internet sources, they collected parliamentary party data for 189 countries after two elections: a stimulus election in the mid-2000s and an adjacent referent election usually held prior to the stimulus election. The authors identified fifteen additional countries that did not hold elections for parliamentary parties and eight countries that held nonpartisan elections, seating no deputies by party. Together these 212 countries account for virtually all the variations in party systems across the world.