Missing the ten best days in US shares since 2006 cut the compound annual rate from 11.05% to 6.68%. Missing the ten worst days lifted it to 15.73%. Missing both left 11.18%, which is where staying put already was.
Time in the market means staying invested through every kind of day. Timing the market means trying to step out before the bad ones and back in before the good ones. Neither of the two one-sided results below is something a person could have produced, because the days are named after the fact.
Is time in the market better than timing the market? In US shares, staying invested earned 11.05% a year since 2006. Sitting out both the ten best and the ten worst days earned 11.18%, so the two come out almost level.
Missing the ten best days cut the annual rate from 11.05% to 6.68%, while missing the ten worst days lifted it to 15.73%.
Neither of those is achievable. The days are picked with hindsight, so they sit in the same few weeks.
Seven of the ten best days fell in the same calendar month as one of the ten worst.
How did we test time in the market?
We took SPY (the S&P 500 exchange-traded fund, or ETF), which holds the large US companies in the index, with dividends counted. The window runs from 3 January 2006 to 19 October 2026. That is 5,231 trading days over 20.8 years.
We started with $10,000 and compounded the daily returns. The compound annual rate is the single yearly return that turns a starting sum into an ending sum. We call it the annual rate from here on.
In each case we removed the days named and held cash on those days. Cash earned nothing. We ran four cases: stayed invested, missed the ten best days, missed the ten worst days, missed both. In this article, "US shares" means SPY.
What does missing the best days cost?
Staying invested turned $10,000 into $88,377, an annual rate of 11.05%. Removing the ten best days left $38,348, an annual rate of 6.68%. Those ten days are 0.19% of the 5,231 trading days.
The loss is real. The ending value falls to less than half of the $88,377 from staying invested.
That figure is usually quoted on its own. Its mirror image belongs beside it: removing the ten worst days instead leaves $208,609, an annual rate of 15.73%, more than double the stay-invested result. Chart 1 shows all four cases.
Source: YX Insights price data
The missed-both bar in Chart 1 stands level with the stayed-invested bar. The two one-sided bars sit far apart on either side of them.
What happens when we miss both?
Missing both the ten best and the ten worst days leaves $90,519, an annual rate of 11.18%. Staying invested earned 11.05%. The missed-both case sits 0.13 points above it.
At ten days the two effects come close to offsetting. The table gives all four cases for 10, 20, 30 and 50 days missed.
Days missed | Share of all days | Missed the best | Missed the worst | Missed both |
|---|---|---|---|---|
None | 0% | $88,377, an annual rate of 11.05% | ||
10 | 0.19% | $38,348 (6.68%) | $208,609 (15.73%) | $90,519 (11.18%) |
20 | 0.38% | $23,066 (4.10%) | $359,750 (18.81%) | $93,892 (11.37%) |
30 | 0.57% | $15,318 (2.07%) | $574,846 (21.51%) | $99,633 (11.69%) |
50 | 0.96% | $7,668 (-1.27%) | $1,309,415 (26.42%) | $113,606 (12.40%) |
$10,000 in US shares from 3 January 2006 to 19 October 2026, with dividends counted. Cash earns nothing on the days out. Percentages in brackets are the compound annual rate. Source: YX Insights price data
None of the three removal cases is a strategy. The days are identified after the fact, so sitting out exactly the ten worst, or exactly the ten best, or both, is not something a person could do in advance. The cases measure how tightly the two sets sit together.
Why do the two removals offset?
Of the ten best days, seven fell in the same calendar month as one of the ten worst. The median gap from a best day to the nearest worst day is five trading days.
Chart 2 groups the two sets by episode. Two episodes hold eight of the ten best days and nine of the ten worst.
Source: YX Insights price data
In 2008, the best days were 13, 20 and 28 October, then 13 and 24 November. The worst days that autumn were 29 September, 9 and 15 October, 19 and 20 November, then 1 December. In March 2020, the best days were 13 and 24 March, plus 6 April, while the worst were 9, 12 and 16 March.
Three days sit outside those two episodes. Two are best days, 23 March 2009 and 9 April 2025. The third is the worst day of 8 August 2011.
Large falls and large rebounds arrive in the same stretches, when prices are moving most in both directions. Sitting out one set therefore means sitting out much of the other. Removing a large gain and a large loss of similar size also leaves the compounding close to where it started.
What if we remove more than ten days?
Chart 3 shows the annual rate with 10, 20, 30 and 50 days missed.
Source: YX Insights price data
Missing only the best days takes the annual rate to 4.10% at 20 days, 2.07% at 30 days and -1.27% at 50 days. Missing only the worst days lifts it to 18.81%, 21.51% and 26.42%.
Missing both leaves 11.37% at 20 days, 11.69% at 30 days and 12.40% at 50 days. The offset is not exact. It widens as more days come out, because the worst days outweigh the best ones as the count grows.
At 50 days the missed-both rate sits 1.35 points above staying invested, against 0.13 points at ten. What the missed-both line does is move far less than either one-sided line.
What does the test assume?
Cash earns nothing while out of the market in this test. Paying it interest would lift every removal case. The 50-day cases would gain most, because they spend the most days in cash.
The test covers one fund over one 20.8-year window. A different index or a different window would give different figures. The test makes no forecast.
The test also puts the full $10,000 in on the first day. Our comparison of the lump sum against spreading money in covers the alternative. Our explainer on why the S&P 500 is hard to beat covers the index itself.
The mean of the yearly returns differs from the annual rate, as our explainer on why the compound rate and the average differ shows.
In this test, the big up days and the big down days clustered in the same few weeks, so removing both left the annual rate at 11.18% against 11.05% for staying invested. The one result a person could actually have had is the 11.05%.
Get the next explainer
The Academy is free to read, here on the web. The Long Trend, our free weekly letter, comes by email.
Learn more with YX Insights
This explainer is part of the YX Insights Academy. Each one takes a single idea and checks it against real data.
The same approach runs through everything else we publish:
Systematic Portfolio: ready-made portfolios for Macro & Megacaps and for Commodities. We publish the holdings and every change.
Multi-model Signals: a daily long-or-flat call on every name we cover. Each call shows how strongly our four models agree.
Research: company deep dives, macro commentary and essays on how we test.
Good places to start on the website:
Academy: more explainers like this one.
Start here: get our free weekly letter by email.
Macro & Megacaps Systematic Portfolio and Commodities: the two portfolios in detail.
Track record: live results since 3 August 2026, plus the ten-year backtest.
Upgrade: get the Systematic Portfolio, Multi-model Signals and research in full.
Common questions about time in the market
What does time in the market mean?
Time in the market means staying invested through good and bad days instead of moving in and out. In our test of SPY, the S&P 500 exchange-traded fund, with dividends counted, staying invested from 3 January 2006 to 19 October 2026 earned a compound annual rate of 11.05%. The test makes no forecast.
Does missing the best days really hurt returns?
Missing the ten best days did cut the annual rate from 11.05% to 6.68% in our test, so the loss is real. Missing the ten worst days lifted it to 15.73%, though. Missing both left 11.18%. The two removals largely offset, because the best and worst days fall in the same few weeks.
Can anyone sit out the ten worst days?
No. The ten worst days are identified after the fact, so sitting them out in advance is not possible. The same goes for the ten best. The removal cases in our test measure how tightly the two sets sit together: seven of the ten best days fell in the same calendar month as one of the ten worst.
How close together are the best and worst days?
The median gap from a best day to the nearest worst day is five trading days. In SPY since 2006, seven of the ten best days fell in the same calendar month as one of the ten worst. The clusters sit in autumn 2008 and March 2020.
DISCLAIMER: This article is strictly educational. Any information or analysis in this note is not an offer to sell or the solicitation of an offer to buy any securities. Nothing in this note is intended to be investment advice and nor should it be relied upon to make investment decisions. Any opinions, analyses, or probabilities expressed in this note are those of the author as of the note's date of publication and are subject to change without notice.