Abstract: Industrial organization affects the relative effectiveness of the shareholder wealth maximization norm in maximizing total social wealth. In nations where product markets are not strongly competitive, a strong shareholder primacy norm fits less comfortably with social wealth maximization than elsewhere because, where competition is weak, shareholder primacy induces managers to cut production and raise price more than they otherwise would. Where competition is fierce, managers do not have that option. There is a rough congruence between this inequality of fit and the varying strengths of shareholder primacy norms around the world. In Continental Europe, for example, shareholder primacy norms have been weaker than in the United States. Historically, Europe's fragmented national product markets were less competitive than those in the United States, thereby yielding a fit between their greater skepticism of the norm's value and the structure of their product markets. As Europe's markets integrate, making its product markets more competitive, pressure has arisen to strengthen shareholder norms and institutions.