The Momentum Effect & Stock Markets

Traditional finance theory states that predictability of future stock prices and abnormal profit based on the trading strategies are impossible. But, a number of researchers during 1980's document that stock prices are predictable based on their past returns. In 1993, Jegadeesh and Titman discover medium term momentum in stock prices where past winners continue to outperform past losers by around 1% per month over the period of 3 to 12 months. After that numerous studies document that the momentum effect is a worldwide phenomenon. From different possible explanations of the momentum effect, it seems that neither risk related explanation nor data snooping and flawed methodology is able to provide widely excepted explanation of the phenomenon. The behavioural finance theory with the help of some models, however, appears to provide the best explanations for the momentum effect. These behavioural models are too many and none of these models is superior among others because each model individually contributes to explaining the momentum effect in different markets or different stock types.