This dissertation addresses a question central to politics: whether the ideological orientation of the leaders and parties that govern make a difference for social welfare. A vast social-science literature argues that government ideology matters for policymaking. But this research has focused on OECD countries and devoted much less attention to most of world’s countries, regimes, and population. This narrow focus reflects a lack of data as well as common assumptions that political institutions should curtail or extinguish any effect of governments’ ideologies in the rest of the world. My dissertation overcomes the lack of data with an original ideology dataset and challenges existing assumptions by subjecting them to a comprehensive empirical analysis. The dissertation’s first chapter presents the Global Leader Ideology dataset, which codes the economic ideologies and political parties of chief executives in 182 countries from 1945 or independence to 2019. The dataset distinguishes between chief executives with leftist, centrist, rightist, and no discernible economic ideology, and vastly expands the scope and refines the measurement of existing datasets. The chapter describes the dataset’s contents and coding procedures, and illustrates its uses, such as by demonstrating that researchers’ common assumptions of young and non-democracies as non-ideological or exclusively rightist are incorrect and that most of their governments have an identifiable and often leftist ideology. The chapter thereby outlines a research agenda to study the global effects of governments’ ideologies on policymaking and socioeconomic outcomes. I leverage the ideology data to investigate worldwide differences in market intervention in the second chapter. I expect the ideological orientation of governments to matter because it reflects different beliefs and constituent preferences about how much the state should intervene into the economy to increase social welfare. Using a difference-in-differences approach, I provide robust evidence that – contrary to widespread assumptions – government ideology matters for state ownership, property rights protection, and market regulation in non-OECD countries, as well as in weak and non-democratic states, but not in OECD countries. These findings suggest that politics in OECD countries differs less from the rest of the world as often presumed and that a lack of state capacity and democracy does not extinguish the effect of government ideology. The dissertation’s third chapter revisits the research on redistribution, which has recently explained worldwide differences with varying political institutions, especially regime types, but struggled to explain the large variation within democracies and dictatorships. I argue that focusing on the actors and their ideologies within regimes partially explains these differences in redistribution. Combining my ideology data with novel information on social service provision, difference-in-differences estimates demonstrate that leftist governments provide more equal access to education and the welfare state than rightist governments across and within political regimes. I further find that these effects are more pronounced in dictatorships, where leaders are less constrained by checks and balances. The chapter offers a new explanation of worldwide differences in redistribution and underlines that governments’ ideological orientations deserve further attention in the study of worldwide differences in policies and socioeconomic outcomes.