Missing Just 10 Trading Days Nearly Halved 20 Years of S&P 500 Returns
Real data from 2003–2022: what happened to a $10,000 S&P 500 investment if you missed the 10, 20, or 30 best trading days — and what it tells us about market timing.
Every market downturn produces the same temptation: sell now, wait for things to calm down, and buy back in at the right time. It sounds rational. The data says it is one of the most expensive mistakes an investor can make.
The numbers
J.P. Morgan Asset Management tracks what happens when investors miss the stock market's best days. Here is the result for a $10,000 investment in the S&P 500 from January 1, 2003 to December 31, 2022 (a 20-year period that included two of the worst crashes in modern history):
| Strategy | Ending value |
|---|---|
| Fully invested the entire time | $64,844 |
| Missed the 10 best days | $29,708 |
| Missed the 20 best days | $17,826 |
| Missed the 30 best days | $11,701 |
| Missed the 40 best days | $7,788 |
Miss 10 days out of 5,035 trading days — that is 0.2% of the time — and your $64,844 becomes $29,708. You lose more than half your gains.
Miss 40 days and your $64,844 becomes $7,788. You lost money over 20 years despite the S&P 500 quintupling in value.
Why the best days and worst days are clustered together
Here is the critical insight: the market's best days almost always occur near the market's worst days — in the thick of bear markets and crashes, not during calm bull runs.
- 7 of the 10 best days in the 2003–2022 study occurred during bear markets.
- The single best day of 2020 (+9.4%, March 13) came in the middle of the fastest market crash in history.
- The best day of the 2008 crisis (+11.6%, October 13) occurred when the S&P 500 was down over 40% from its peak.
An investor who "waits for things to calm down" is almost certain to miss these recoveries. By the time the news is good again, the big up-days have already happened.
The psychology trap
Market timing feels safe because it is action-oriented. Staying invested during a crash feels passive and frightening. But the data consistently shows that investors who act on fear — selling during downturns and waiting for recovery — perform significantly worse than those who simply hold.
Dalbar's annual Quantitative Analysis of Investor Behavior (QAIB) shows the average equity investor has historically earned roughly 3–4% per year compared to the S&P 500's ~10%. The gap is almost entirely explained by poorly timed entries and exits.
What to do instead
The alternative is straightforward:
- Stay invested through market downturns.
- Keep adding to your portfolio on a fixed schedule (dollar-cost averaging), so you buy more shares when prices are lower.
- Focus on the business, not the price. If the underlying company is fundamentally sound, a temporary price decline is not a reason to sell.
The 20-year study is clear: the cost of missing the market's best days dramatically outweighs any benefit from avoiding its worst. The solution is not to be in the market for the good times and out for the bad times — no one can consistently do that. The solution is to simply stay in.