Why selling in a panic usually locks losses in, and what the evidence describes as a calm counterweight.
A red screen trips an old reflex: get out, get to safety, now. Yet in a crash that reflex is rarely an ally. The data suggest that selling in a panic tends to lock losses in rather than limit them. What truly carries you through a downturn is less a clever decision in the moment than a rule that was settled long before.
The appeal of selling in a crash lies in its promise: you make the pain smaller through action. The evidence argues otherwise. An MIT study (Elkind, Kaminski, Lo and others, Journal of Financial Data Science 2022) examined 653,455 accounts from 298,556 households. A panic sale was defined as an account whose equity holdings fell by 90 percent within a single month, with at least half of that fall driven by active selling.
The study's central finding is sobering: the median investor earned a return of zero to negative after a panic sale. The reason lies not in the sale alone but in what comes after. Whoever sells in a panic typically waits too long to re-enter and so misses the recovery. The study also observes that almost a third of panic sellers never return to risky assets at all.
Selling is the easy half of the decision. The hard half, the right moment to re-enter, rarely arrives.
This shifts where the real problem sits. The question is not whether the sale avoids the next day of losses. It is that after the exit you must make a second, far harder decision, and that second decision, in experience, comes too late.
The pressure to act in a downturn is not a character flaw. It is deeply wired. Kahneman and Tversky described loss aversion in 1979: for most people, losses feel roughly twice as strong as an equal-sized gain. A falling portfolio balance therefore generates a pressure to act that bears no proportion to the actual financial movement.
This asymmetry explains why calm intentions evaporate when it counts. As long as prices are rising, sitting still seems self-evident. The moment they fall, a system speaks up that places quick relief above long-term logic. Anyone who knows this can counter it, though most effectively before the stress sets in, not in the middle of it.
From the observation that sitting still helps follows a tempting but dangerous refinement: surely one could avoid the bad days and keep only the good ones. The data from J.P. Morgan Asset Management show how expensive it is to miss the best days. For the S&P 500 over the twenty years from July 2004 to July 2024, the picture is as follows.
The data point in a different direction. An MIT study observes that the median investor earns a return of zero to negative after a panic sale, because re-entry usually comes too late and the recovery is missed. Rather than a decision under stress, a rule fixed in advance tends to help more. This is general education, not individual advice.
In practice, hardly. According to J.P. Morgan Asset Management, seven of the ten best days fell within fifteen days of the ten worst, and nine of the ten best fell in recessions according to the Wells Fargo Investment Institute. Whoever exits to avoid the bad days, with high probability misses the best ones too. The lesson is to stay invested. This is general education, not individual advice.
Four building blocks fixed in advance: a written rulebook (Vanguard estimates the behavioural contribution at about 1.5 percent per year, an estimate), automatic rebalancing (which lowers risk at a similar return, per Vanguard), a cash buffer that makes selling in a crash unnecessary, and a still-running savings plan that lowers the average price in falling markets.
| Scenario | Return per year |
|---|---|
| Fully invested throughout | 10.5 % |
| Missed the 10 best days | 6.2 % |
| Missed the 20 best days | 3.6 % |
| Missed the 30 best days | 1.4 % |
This figure must never stand alone, however. For the best days lie close beside the worst and occur predominantly in falling markets. J.P. Morgan observes that seven of the ten best days fell within fifteen days of the ten worst days. The Wells Fargo Investment Institute finds, for the S&P 500 between 1995 and 2025, that nine of the ten best days fell in recessions.
A crash feels like a fall with no floor. The historical view puts that in perspective without promising anything. Data from Hartford Funds for the S&P 500 since 1929 show that an average bear market was about minus 35 percent over roughly 289 days. The four large declines of recent history ran to different depths and different lengths. The table shows only the depth and duration of the declines; the recovery times varied widely.
| Bear market | Decline | Duration |
|---|---|---|
| 1987 | –33.51 % | 101 days |
| 2000 to 2002 | –36.77 % | 546 days |
| 2008 to 2009 | –51.93 % | 408 days |
| 2020 | –33.92 % | 33 days |
Over the past roughly 95 years, stocks rose about 78 percent of the time. Historically, past declines have recovered, provided enough time passed. That is an observation about the past, not a promise about the future: the pace and extent of the next recovery are not guaranteed, and the range above, from 33 to 546 days, shows how little the exact path can be predicted.
When the moment itself is unreliable, the decision must move ahead of the moment. Four building blocks have proven themselves, supported by data, as calm counterweights.
A written rulebook, fixed in advance. A rule set out beforehand denies the panic its stage, because the decision is already made. Vanguard estimates, in its Advisor's Alpha research, that behavioural coaching, there in the context of advice, can contribute roughly 150 basis points (1.5 percent per year). This value accrues unevenly, above all in turbulent phases, and is an estimate, not a promise. Yet it points to the largest lever: your own behaviour.
Automatic rebalancing. Whoever defines fixed thresholds and mechanically returns to them buys more in a downturn instead of selling in a panic. Vanguard compared two approaches for a 60/40 portfolio from 1926 to 2009.
| Approach | Return | Risk |
|---|---|---|
| Rebalanced annually | 8.6 % | 11.9 % |
| Never rebalanced | 9.1 % | 14.4 % |
The returns lie close together, the risk noticeably apart. Rebalancing cost about 0.5 percentage points of return per year here and at the same time lowered the risk markedly: a deliberate trade of a little return for calmer swings, one that also forces countercyclical buying at the lows.
A liquidity buffer. From the MIT finding it follows logically: whoever needs no cash in a crash need not sell any stocks. A cash buffer for ongoing expenses takes away the market's power to force you to the table at the least favourable moment.
Keep the savings plan running. Each instalment buys at lower prices in falling markets and so lowers the average price, which softens the loss but does not rule it out if prices keep falling. The savings plan quietly turns falling prices into an advantage, provided it simply keeps running.
Kernaussagen
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A written rulebook, in Investboard your Mandat, and a cooling-off pause are meant to keep the plan calm when prices fall. In Investboard you anchor both in advance.
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