Asian Review of Financial Research Vol.30 No.3 pp.317-359
Price Momentum Anomaly Revisited : Evidence in the Korean Stock Market
Key Words : Momentum,Intermediate Horizon Past Returns,Anomaly,Cross-Section Of Stock Returns,Korean Stock Market
This study examines whether price momentum is driven by firms' recent past performance or intermediate horizon past performance in the Korean stock market. Price momentum, a tendency of rising and falling stocks to keep rising and falling, is one of the most well-known stock market anomalies, and an extensive body of literature has shown that momentum is widely observed across a variety of countries and asset classes. However, previous studies provide the particularly interesting result that momentum is not strongly observed in the Korean stock market, and this is seen as exceptional. Several recent studies suggest that momentum strategies based on ranking or holding periods longer than six months were profitable in Korea in the period after the 1997 Asian financial crisis. Given these results and motivated by the recent empirical finding of Novy-Marx (2012, Is momentum really momentum? Journal of Financial Economics 103, 429-453) that momentum is primarily driven by intermediate past performance rather than by recent past performance, in this study, I examine whether the period over which past performance is measured plays an important role in determining the profitability of momentum strategies in the Korean stock market. I use monthly data for ordinary common stocks listed on the Korean Stock Exchange over the period February 1999 to December 2015. The main empirical findings are summarized as follows. First, momentum strategies based on performance during the period from 12 to seven months prior to portfolio formation earn positive and significant abnormal returns, while momentum strategies based on performance during the recent six months do not yield significant profits. The zero-cost portfolio buying the top 10% and selling the bottom 10% stocks based on intermediate past performance yields a Fama-French (1993) three-factor alpha of 1.51% per month, with a t-statistic of 2.06. The intermediate past performance can predict stock returns in the cross-section even after controlling for various firm characteristics, including firm size, the book-to-market ratio, idiosyncratic volatility, illiquidity, and turnover. Second, the abnormal profits of momentum strategies based on performance during the past 12 months are entirely driven by intermediate past performance, not by recent past performance. The past 12-month return loses its predictive power for the cross-section of stock returns after controlling for past returns during the period from prior 12 to seven months. At the same time, the predictive power of intermediate past returns is not affected by recent past returns. Stocks that are recent six-month winners but past 12-to-seven-month losers earn abnormally low returns on average. Third, the momentum anomaly based on intermediate past performance is more pronounced for stocks with a smaller size, higher liquidity, higher proportion of individual trading, and higher analyst coverage. The roles of liquidity and analyst coverage are not easily explained if momentum based on intermediate past performance was due to mispricing, because arbitrage is more likely to be limited for stocks with lower liquidity and lower analyst coverage. Finally, the abnormal profits of momentum strategies based on intermediate past performance are positive and significant only following periods of high aggregate liquidity and high stock market returns, but they are insignificant after periods of low aggregate liquidity and low stock market returns. This result suggests that momentum based on intermediate past performance could be at least partially due to a change in economic states. This study contributes to the literature on the cross-section of returns in the Korean stock market in the following ways. First, it is the first to investigate whether intermediate horizon past performance can predict the cross-section of returns in Korea. Previous studies on price momentum in the Korean stock market have focused on the predictive power of recent past performance and found only weak evidence that momentum profits are partially significant for stocks with particular characteristics or during particular periods. This study provides strong evidence that momentum strategies based on intermediate past performance yield significant and positive abnormal profits during the post-crisis period. Second, the empirical findings of this study help to reconcile conflicting results in the literature. It has been widely believed that momentum is relatively weak in Korea because momentum strategies based on past performance measured over no longer than six months are not profitable, which stands in contrast to the strong profitability of momentum strategies in the U.S. market. This study finds evidence that based on intermediate past performance, momentum strategies also become as profitable in the Korean stock market as in the U.S market. Although the profitability of momentum strategies based on recent past performance differs, intermediate past performance can significantly predict the cross-section of stock returns in both markets. These results suggest that price momentum cannot be simply interpreted as a short-run autocorrelation in returns and emphasize the importance of information in intermediate-horizon past performance.