Abstract: Fiscal federalism is commonly held to reduce the size of government, but how does it do so: through shrinking the welfare state, cutting government consumption, or reducing public investment? This paper examines tax competition under fiscal federalism through the lens of imperfect competition theory, derives new empirical implications from different theories of fiscal federalism, and tests those hypotheses with new variables and data. Cross-national statistical results show that jurisdictional competition under fiscal federalism is associated with reductions in the administrative expense of government but not the size of the welfare state. Moreover, the apparent impact of fiscal federalism with a high degree of jurisdictional competition is larger than that estimated in previous research. Once the models have been appropriately specified, the United States is no longer an outlier among high-income democracies on either government consumption or social spending. Close examination of the data reveals that some fiscally federal systems better approximate a “market-preserving model” and others a “capital-privileging” or “state-corroding” model.