Price Momentum in Korea and the Effect of Investors’ Trading

This study investigates domestic individual, institutional and foreign investors’ trading, to test Hong and Stein (1999)’s behavioral explanation that momentum profit is generated as some uninformed investors underreact to information on medium-term prices. Using Hvidkjaer (2006)’s methodology, we examine the respective investors’ trading tendencies reflected in their active price-setting orders. We analyze a special database compiling details on every transaction for the stocks listed on the KSE during 1996:12~2009:08. During 2001~2007, individual investors’ underreaction in trading large-size winner stocks contributes to positive momentum profits. They seem to induce weak negative profits to emerge in 1997~2000, too. Foreign investors underreact to small-size loser stocks, incurring positive momentum profits during 2001~2007. They engage in positive feedback trading, when they trade large-size winner stocks. This trading tendency does not seem to be based on information on firm fundamentals, as we find those winner stocks’ returns are not sustained. Institutional investors’ trading seems to be relatively in line with future returns, but evidences are not strong enough to support they are informed investors. Overall, the behavioral hypothesis on investors’ underreaction seems to explain medium-term momentum profits in Korea, but evidences differing across subsamples suggest possibility of other unknown influences.