The saying is old and it rhymes, which is exactly why it survives. Sell in May and go away, come back on St. Leger's Day. It traces back to a London horse race from 1776.
The claim is simple. November through April has historically been the stronger six month stretch for stocks, while May through October has lagged behind.
The historical numbers behind the saying
There's real data supporting this pattern, not just folklore. Since 1945, the S&P 500 has gained nearly 7% in the six month period from late October through April, rising in price 75% of the time.
May through October tells a weaker story by comparison. From 1999 to 2025, average monthly returns during that stretch sat around 0.69%, versus roughly 1.03% for the November through April window.
Where the strategy holds up
The pattern isn't invented. It shows up across multiple time frames and multiple data providers, which is why it keeps getting repeated every spring.
November through April has been the strongest rolling six month period going back decades.
May through October returns have historically stayed positive most years, just weaker.
Defensive sectors like utilities and health care tend to hold up better during the weak months than cyclical sectors like technology and financials do.
This is where the concept of a defensive stock earns its keep. These names are built to absorb weaker seasonal stretches better than growth-driven sectors.
Why the pattern exists in the first place
Lower summer trading volume, fewer institutional catalysts, and a historical clustering of downturns in August and September all feed into the pattern. None of it is mysterious. It's mostly about reduced activity, not some hidden market law.
Where the strategy completely falls apart
Here's the problem nobody puts on the bumper sticker. Actually executing "sell in May" destroys long term returns compared to just staying invested.
An investor who put $1,000 into the S&P 500 in January 1976 and held it through 2025 would have ended up with $294,795 using a straightforward buy and hold approach. An investor who sold every April 30 and reinvested every November 1 for the same 50 years would have ended with only $46,351.
That gap isn't small. It's the difference between a strategy that compounds properly and one that keeps interrupting compounding at exactly the wrong moments.
Why timing kills more than it protects
Every time you sell, you're betting you'll re-enter at a better price later. Missing just the market's 20 best trading days over that same 50 year window would have cut the ending balance to $72,599, less than a quarter of what buy and hold delivered.
Market timing sounds protective. In practice it usually swaps a manageable seasonal dip for a much bigger structural cost.
Why recent years break the old pattern
The last decade hasn't cooperated with the adage either. Since 2013, May itself has averaged a 1.5% gain, with 12 of the last 13 years finishing positive. The "weak" months keep showing up strong, which undercuts the whole premise of stepping aside.
What to actually take from the seasonal pattern
The lesson isn't that seasonality is fake. It's that seasonality is a mild statistical tilt, not a trading system.
Use the pattern as context for expected volatility, not a signal to exit.
Lean slightly toward defensive sectors during summer if you want to express the idea at all.
Never treat six months out of the market as a low risk decision. It carries real opportunity cost.
Keep contributions running through the "weak" months instead of pausing them.
Investors following a strict buy and hold philosophy have historically outperformed anyone trying to dodge the calendar.
What actually survives the sell in May test
The saying gets the historical averages roughly right. It gets the practical advice badly wrong. Stepping out of the market for six months every year has cost far more in missed compounding than it's ever saved in avoided dips. Respect the pattern as a data point. Don't build a strategy around it.
This article is for informational purposes only and does not constitute financial advice.
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