# Market Overreaction: Why Prior Losers Outperform Prior Winners

Cite as: Gorak, R. (2026). Market Overreaction: Why Prior Losers Outperform Prior Winners. Tradicted. https://www.tradicted.com/research/bondt-overreaction-1985/
Paper: Werner F. M. De Bondt and Richard Thaler — *Does the Stock Market Overreact?*
Published in: Journal of Finance (1985)
Original: https://www.jstor.org/stable/2327804

Key finding: Over the last half-century, loser portfolios of 35 NYSE stocks outperform the market by 19.6% thirty-six months after portfolio formation, while winner portfolios earn about 5.0% below the market, yielding a return spread of 24.6% (t-statistic: 2.20) in favor of prior losers.

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De Bondt and Thaler's (1985) "Does the Stock Market Overreact?" tests whether investors push prices too far past fundamental value. Their dataset is the CRSP Monthly Return File, covering 347–1,089 NYSE stocks between January 1926 and December 1982. Loser portfolios of 35 stocks outperformed the market by 19.6%, and winner portfolios underperformed by about 5.0%, over 36 months. The return spread [ACARL,36 − ACARW,36] = 24.6% (t-statistic: 2.20) across 16 non-overlapping three-year periods.

## What the Study Found

Loser portfolios of 35 stocks earned 19.6% above the market over 36 months; winner portfolios earned about 5.0% below. The [ACARL,36 − ACARW,36] = 24.6% (t-statistic: 2.20) spans 16 non-overlapping 3-year test periods. The overreaction effect is asymmetric: losers drive most of the spread, with January excess returns of 8.1% (t=3.21) at month t=1. Loser January returns persist: 5.6% (t=3.07) at month 13 and 4.0% (t=2.76) at month 25. Twelve months into the test period, the return spread is only 5.4% (t=0.77).

## Methodology

De Bondt and Thaler (1985) use the CRSP Monthly Return File for all NYSE common stocks from January 1926 to December 1982. Between 347 and 1,089 NYSE stocks participate per replication across 16 non-overlapping 3-year formation periods (January 1930 – December 1977). Winner and loser portfolios are the top and bottom 35 stocks by prior 36-month market-adjusted excess returns. Primary residuals are market-adjusted (u_{jt} = R_{jt} − R_{mt}); the study also tests market model and Sharpe-Lintner CAPM residuals.

## Key Statistics

| Metric | Finding | Context |
|---|---|---|
| ACARL,36 − ACARW,36 | 24.6% (t=2.20) | 16 three-year periods, 35 stocks, test period end |
| Loser portfolio ACAR at 36 months | 19.6% above market | 16 three-year periods, 35 stocks |
| Winner portfolio ACAR at 36 months | about 5.0% below market | 16 three-year periods, 35 stocks |
| January excess return — month t=1 | 8.1% (t=3.21) | Loser portfolio, 16 three-year periods |
| January excess return — month t=13 | 5.6% (t=3.07) | Loser portfolio, 16 three-year periods |
| January excess return — month t=25 | 4.0% (t=2.76) | Loser portfolio, 16 three-year periods |
| Return spread at 12 months | 5.4% (t=0.77) | Not statistically significant; reversal concentrated in years 2–3 |
| Winner portfolio CAPM beta | 1.369 | 3-year experiment; t-statistic on difference vs. loser: 3.09 |
| Loser portfolio CAPM beta | 1.026 | 3-year experiment; winners are significantly more risky |
| ACARL,60 − ACARW,60 (5-year formation) | 0.319 (t=3.28) | 10 five-year periods, 50 stocks |

## Why This Matters

Loser portfolios carry lower CAPM betas than winners, so risk-adjusted returns understate the true overreaction spread. The reversal concentrates in January of years two and three, not year one, which raises questions beyond tax-loss selling as a full explanation. The results challenge weak-form market efficiency: past return data alone predict future returns without any fundamental information. De Bondt and Thaler trace the pattern to Kahneman and Tversky's representativeness heuristic, connecting laboratory psychology to aggregate market prices.

## FAQ

### What is the stock market overreaction effect?

24.6%: that is the cumulative average residual spread between prior losers and winners at 36 months in De Bondt and Thaler (1985). Stocks that previously underperformed subsequently outperform stocks that previously outperformed. The authors attribute this to investors overreacting to news in violation of Bayes' rule.

### How large is the contrarian return premium?

19.6%: the cumulative market-adjusted excess return for the loser portfolio at 36 months. Winner portfolios earn about 5.0% below the market over the same period. The 24.6% spread (t-statistic: 2.20) covers 16 non-overlapping 3-year test periods running January 1933 to December 1980 (the corresponding formation periods ran January 1930 to December 1977).

### Is the return reversal explained by differences in market risk?

1.369 versus 1.026: those are the CAPM betas for winner and loser portfolios in the 3-year experiment (t-statistic on difference: 3.09). Loser portfolios are significantly less risky than winner portfolios by this measure. If CAPM is correct, market-adjusted returns understate the true magnitude of the overreaction effect.

### How persistent is the January return on loser portfolios?

8.1% is the excess return earned by the loser portfolio in January of the first test year (month t=1; t-statistic: 3.21). The January effect persists: 5.6% (t=3.07) at month 13 and 4.0% (t=2.76) at month 25 — as late as five years after portfolio formation.

## Source

De Bondt, W. F. M. and Thaler, R. (1985). Does the Stock Market Overreact? *Journal of Finance*, 40(3), 793–805.

[Read the full paper →](https://www.jstor.org/stable/2327804)