Paper Trail #3: The Disposition Effect (Odean, 1998)
Ten thousand discount-brokerage accounts. Seven years of trading records (1987-1993). Two ratios per account. And one uncomfortable finding: retail investors realized 50% more of their winners than their losers, and the winners they sold went on to outperform the losers they held by +3.4% over the following year.
This is Paper Trail #3. Same rules: every claim comes from the paper itself, verified against a copy I actually opened.
The paper
Odean, T. (1998).“Are Investors Reluctant to Realize Their Losses?” The Journal of Finance, Vol. LIII, No. 5 (October 1998), pp. 1775-1798. DOI 10.1111/0022-1082.00072.
Odean got trading records from a large US discount brokerage for the period January 1987 through December 1993: 10,000 accounts, and (in the positions file starting January 1988) 1,258,135 monthly position records. Roughly 20% of the accounts were IRAs or Keogh accounts (tax-exempt); the remaining 80%were taxable. The paper’s core question: do these retail investors actually behave the way Shefrin and Statman (1985) proposed — holding losers too long and selling winners too soon — when you look at their real trades? Answer: yes, and here’s the arithmetic.
PGR and PLR — the two ratios
On any day an account sells at least one stock, define:
PGR = realized gains / (realized gains + paper gains)
PLR = realized losses / (realized losses + paper losses)
In words: of all the gains you could have realized today, what fraction did you realize? Same question for losses. If you care equally about the two, PGR should equal PLR. If you have a strong preference for one over the other, they diverge.
Aggregate across every account and every trading day in the sample:
| Period | PLR | PGR | Difference | t-stat |
|---|---|---|---|---|
| Entire year | 0.098 | 0.148 | −0.050 | −35 |
| December | 0.128 | 0.108 | +0.020 | +4.3 |
| January-November | 0.094 | 0.152 | −0.058 | −38 |
The entire-year line is the paper’s headline claim. PGR is 0.148 and PLR is 0.098 — investors were ~50% more likely to realize an available gain than an available loss. The t-statistic is -35, which by any statistical standard is a landslide.
The December flip
Read the second and third rows carefully. The January-through-November subset makes the disposition effect look even stronger (difference -0.058, t = -38). But December alone inverts: PLR 0.128 exceeds PGR 0.108, difference +0.020, t = +4.3.
That’s the tax-loss-selling deadline flipping the pattern. Investors don’t losetheir disposition-effect behavior in December — they override it because that’s the last month to book losses against the tax year. Figure 2 in the paper plots the PGR/PLR ratio month by month; it starts at 2.1 in January and falls monotonically to 0.85 in December. Behavior consistent with the Shefrin-Statman story: sell losses reluctantly, then in a burst at the deadline.
The ex-post return finding — why this matters
Odean’s Table VI does the follow-through. Take every winner sale in the sample and calculate the excess return of the sold stock over the CRSP value-weighted index for the next N trading days. Do the same for every paper loss (a loss that could have been but wasn’t realized). Compare.
| Horizon | Sold winners | Kept losers | Difference | p-value |
|---|---|---|---|---|
| Next 84 trading days | +0.47% | −0.56% | +1.03% | 0.002 |
| Next 252 (1 year) | +2.35% | −1.06% | +3.41% | 0.001 |
| Next 504 (2 years) | +6.45% | +2.87% | +3.58% | 0.014 |
The sold winners kept winning. The kept losers kept losing. The difference is +3.4 percentage points at the one-year horizon (p = 0.001) — highly statistically significant even after Odean’s bootstrap re-sampling adjustment. Investors who sold winners and held losers because they expected the losers to bounce back were, on average, wrong.
Odean notes (page 1787) that the winner-outperformance direction is consistent with Jegadeesh & Titman’s (1993) momentum finding — the paper we covered in Paper Trail #2. Sold winners were winners for a reason; that reason continued to work for months.
Why the disposition effect happens (short version)
The paper opens Section I.A with the prospect-theory interpretation — the framework from Kahneman & Tversky (1979), which we covered in Paper Trail #1. Under prospect theory, investors evaluate outcomes relative to a reference point (the purchase price), and the value function is concave in the gain domain (diminishing marginal utility of more gains, pushing toward realization) and convexin the loss domain (a “maybe it comes back” risk-loving posture, pushing toward holding). The two effects push in the same direction on gains and losses respectively: sell winners, hold losers. That prediction is exactly what Odean documented empirically.
The paper ruled out three obvious alternative explanations before landing on prospect theory:
- Rebalancing. Restricting the analysis to sales that closed the entire position (i.e. weren’t rebalancing trims) — the effect persisted.
- Transaction costs at low prices. Splitting the analysis by price range — the effect persisted at every price range.
- Rational belief that losers will bounce. Killed by Table VI. Held losers didn’t bounce — they underperformed the sold winners by 3.4pp over the next year.
What this doesn’t say (my extrapolation)
The paper is a study of US retail equity trading at a single discount broker, 1987-1993. Three specific limits.
It doesn’t say every trader has this problem. Odean reports (page 1786) that the most active 10% of traders account for 57%of all trades in the sample — but doesn’t claim they’re free of the disposition effect. The aggregate PGR-PLR gap is population-level, not per-trader; some traders will be much worse than the average and others notably better.
It doesn’t say the same thing happens in FX. The paper is about individual US stocks with holding periods measured in months. FX retail trading typically involves shorter holding periods, leverage, and no long-term-capital-gains tax treatment — the December flip mechanism doesn’t exist in the same form. There isa subsequent literature on the disposition effect in FX (Locke & Mann 2005 on floor traders, for example, and various retail-broker studies), but the specific 3.4pp underperformance number is a stocks number from 1987-1993, not a universal claim.
It doesn’t say “always sell losers, never sell winners.”The paper documents an aggregate bias, not a per-trade rule. Any specific loss you’re holding may still bounce back; Odean’s point is that on average and over a large enough sample the “let it recover” strategy underperforms the “cut the loser, keep the winner” strategy — which is exactly the opposite of what typical retail behavior actually does.
Why it’s useful anyway
Odean’s paper is one of the strongest “behavioral finance meets a real ledger” results — a specific, falsifiable, and later replicated claim about how retail investors actually trade, drawn from 1.26 million monthly position records rather than from a lab experiment or a survey. Every trader looking at their own P&L should at least ask the question the paper asks: on days when I sold a stock, was I more willing to close a winner or a loser? A quick own-ledger PGR/PLR calculation is a two-line exercise, and the answer is usually interesting even if it’s not the -0.050 that the paper found aggregated across 10,000 accounts.
The 3.4pp follow-through matters more than the disposition effect itself. The effect is uncomfortable; being wrong about it is expensive. If your holding pattern looks like Odean’s average trader’s and your held losers act like his did, that’s a percentage-point return leak you can measure — and adjust for — without changing anything about the individual trades.