Around the world, nationalist politicians see migrants and ethnic minorities as undeserved receivers of public goods. What underpins these exclusionary claims is the thesis that ethnic diversity impedes the prospects of economic progress and social welfare. Does this thesis withstand systematic inquiry? At a first glance, there are plenty of studies that link ethnic heterogeneity to the underprovision of public goods. An influential literature in political economy asserts a strong association between high levels of diversity and low levels of public service provision such as schooling or health care. States, Nationalism, and the Relationship between Ethnic Diversity and Public Goods Provision [ETHNICGOODS] aims to revisit and challenge this conventional wisdom, and the doggedly ahistorical perspective it implies. Instead of treating ethnic diversity as exogenous, the project explores the role of historical patterns of nation-building and state institutional development. I expect different nation-building modes—that is, whether states seek to assimilate, accommodate, or exclude minorities—to have distinct consequences for contemporary levels of diversity and collective goods provision. I further expect historical variations in the capacity of states to provide public goods to affect contemporary levels of heterogeneity and public goods provision. To develop and test this theoretical argument on a global scale, ETHNICGOODS will create two new, publicly available datasets and combine comparative-historical case studies and statistical analysis. With this ambitious focus the project aims to make a major contribution to our understanding of ethnic diversity, injecting a historical perspective into debates around the political and developmental consequences of heterogeneity. Finally, by connecting with a range of academic and non-academic audiences, ETHNICGOODS will influence public debates about ethnic diversity and its effects.