ABSTRACT Portfolio allocation decisions increasingly incorporate social values. We develop a tractable framework to study how competition between investors to own socially valuable assets affects social welfare. Relative to the most common social‐investing strategies, we identify alternative strategies that result in higher impact and higher financial returns. We identify strategies for investors to have impact when impact is difficult to measure. From the firm's perspective, increasing profitability can have greater impact than directly increasing social value. We present new empirical evidence on the social preferences of investors that demonstrates the practical relevance of our theory.