Is shareholder interest in corporate social responsibility driven by pecuniary motives (abnormal rates of return) or nonpecuniary ones (willingness to sacrifice returns to address various firm externalities)? To answer this question, we summarize the literature by focusing on seven tests: ( a) costs of capital, ( b) performance of portfolios, ( c) ownership by types of institutions, ( d) surveys and experiments, ( e) managerial motives, ( f) shareholder proposals, and ( g) firm inclusion in responsibility indices. These tests predominantly indicate that shareholders are driven by nonpecuniary motives. To stimulate further research on welfare implications for global warming, we assess whether estimates of the foregone returns for shareholders willing to reduce carbon emissions (or “greeniums”), along with the wealth pledged to firms that become sustainable, are consistent with the growth of aggregate investments in the decarbonization sector.