Calvo, Guillermo A.Mendoza, Enrique G.This paper argues that globalization may promote contagion by weakening incentives for gathering costly information and by strengthening incentives for imitating arbitrary market portfolios. In the presence of short-selling constraints, the gain of gathering information at a fixed cost may diminish as markets grow. Moreover, if a portfolio manager’s marginal cost for yielding below-market returns exceeds the marginal gain for above-market returns, there is a range of optimal portfolios in which all investors imitate arbitrary market portfolios and this range widens as the market grows. Numerical simulations suggest that these frictions can have significant implications for capital flows in emerging markets.en-USHerd behaviorcontagioncapital mobilityinternational portfolio diversificationArticle