This article examines whether the efficiency gains accompanying fiscal decentralization generate higher growth in more decentralized economies, applying pooled-mean group techniques to a panel dataset of 23 Organization for Economic Co-operation and Development (OECD) countries, 1972–2005. We find that spending decentralization has tended to be associated with lower economic growth while revenue decentralization has been associated with higher growth. Since OECD countries are substantially more spending than revenue decentralized, this is consistent with Oates' (1972) hypothesis that maximum efficiency gains require a close match between spending and revenue decentralization. It suggests reducing expenditure decentralization, and simultaneously increasing the fraction financed locally, would be growth-enhancing. (JEL E62, H71, H72)