41 Pages Posted: 27 Apr 2000
Date Written: May 1989
The profitability of contrarian investment strategies need not be the result of stock market overreaction. Even if returns on individual securities are temporally independent, portfolio strategies that attempt to exploit return reversals may still earn positive expected profits. This is due to the effects of cross-autocovariances from which contrarian strategies inadvertently benefit. We provide an informal taxonomy of return-generating processes that yield positive [and negative] expected profits under a particular contrarian portfolio strategy, and use this taxonomy to reconcile the empirical findings of weak negative autocorrelation for returns on individual stocks with the strong positive autocorrelation of portfolio returns. We present empirical evidence against overreaction as the primary source of contrarian profits, and show the presence of important lead-lag relations across securities.
Suggested Citation: Suggested Citation
Lo, Andrew W. and Mackinlay, A. Craig, When are Contrarian Profits Due to Stock Market Overreaction? (May 1989). NBER Working Paper No. w2977. Available at SSRN: https://ssrn.com/abstract=227214
By Andrew Lo
By Andrew Lo