This paper analyzes the trading behavior of stock market investors. Purchases and sales are highly correlated when we divide investors geographically. Investors who live near a firm's headquarters react in a similar manner to releases of public information. We are able to make this identification by exploiting a unique feature of individual brokerage accounts in the People's Republic of China. The data allow us to pinpoint an investor's location at the time he or she places a trade. Our results are consistent with a simple, rational expectations model of heterogeneously informed investors.