"Using holdings data on a representative sample of all Shanghai Stock Exchange investors, we show that increases in the fraction of market participants who own a stock predict low returns: highest change quintile stocks underperform lowest quintile stocks by 23 percent per year. This is consistent with ownership breadth primarily reflecting popularity among noise traders rather than the amount of negative information excluded from prices by short-sales constraints. But stocks in the top decile of wealth-weighted institutional breadth change outperform the bottom decile by 8 percent per year, suggesting that breadth measured among sophisticated institutional investors who cannot short does reflect missing negative information. The profitability of institutional trades against retail investors is almost entirely explained by their correlations with retail and institutional breadth changes. In the time series, average breadth changes negatively predict aggregate stock market returns"--National Bureau of Economic Research web site.