Do foreign investors improve informational efficiency of stock prices? Evidence from Japan

• Increase in foreign ownership is associated with increased price efficiency in Japan.
• Foreign ownership change predicts price efficiency change in Granger causality test.
• A quasi-natural experiment finds consistent evidence.

This study investigates the impact of foreign investors on the informational efficiency of stock prices in local markets. Using a large sample of Japanese firms over the period 1976 to 2008, we find that prices deviate less from a random walk for stocks with a large change in foreign ownership. This relation is robust to controls for local institutional ownership, stock liquidity, and firm fixed effects. Granger causality tests show that changes in foreign investor trading predict changes in price efficiency in the next period, but not vice versa. Finally, we use a quasi-natural experiment to show that an increase in foreign ownership causes an improvement in price efficiency. Collectively, these results suggest that foreign investors improve price efficiency in local stock markets.