An Epidemic Model of Investor Behavior
用传染病传播模型衡量社会影响，发现芬兰20只最活跃股票中，社会接触驱动的交易能预测个股回报，且效果不可逆，说明投资者在分享有用信息。
Abstract I test whether social influence affects individual investors’ trading and stock returns. In each of the 20 most active stocks in Finland over 9 years, the number of owners in a municipality multiplied by the number of investors who do not own a stock, a measure of the rate of transmission of diseases and rumors through social contact, predicts individual investor trading. I control for known determinants of trade, including daily news, and show that competing explanations for the relation are unlikely. Socially motivated trades predict stock returns, and the effects are not reversed, suggesting that individuals share useful information. Individuals’ susceptibility to social influence has declined during the period, but the opportunities for social influence have increased.