This dissertation consists of three essays on the role of social values in financial markets. Chapter 1 uses geographic variation in religious concentration to identify the effect of people's gambling behavior in financial market settings. We argue that religious background predicts people's gambling propensity, and that gambling propensity carries over into their behavior in financial markets. We test this conjecture in various financial market settings and find that the predominant local religion predicts variation in investors' propensity to hold stocks with lottery features, in the prevalence of broad-based employee stock option plans, in first-day returns to initial public offerings, and in the magnitude of the negative lottery-stock return premium. Collectively, our findings indicate that religious beliefs regarding the acceptability of gambling impact investors' portfolio choices, corporate decisions, and stock returns. In Chapter 2 I examine the impact of social norms against holding certain types of stocks (e.g. "sin stocks", or stocks with lottery features) on trading decisions and portfolio performance. I argue that trades which deviate from social norms are likely to reflect stronger information. Consistent with this hypothesis, I find that the most gambling-averse institutions earn high abnormal returns on their holdings of lottery stocks, outperforming the holdings of the most gambling-tolerant institutions. An analysis of institutions' sin stock holdings provides complementary evidence using another dimension of social norms, supporting the hypothesis that trades which deviate from norms reflect stronger information. In the third essay, we conjecture that people feel more optimistic about the economy and stock market when their own political party is in power. We find supporting evidence from Gallup survey data and analyze brokerage account data to confirm the impact of time-varying optimism on investors' portfolio choices. When the political climate is aligned with their political preferences, investors maintain higher systematic risk exposure while trading less frequently. When the opposite party is in power, investors exhibit stronger behavioral biases and make worse investment decisions. Investors improve their raw portfolio performance when their own party is in power, but the risk-adjusted improvement is economically small.