‘Sell in May’ Looks to Be Going Astray. Again.

When do the “summer doldrums” supposedly start? One month ago, an old investment adage says we should all have dumped our stock portfolios, enjoyed life while stocks wobbled for the summer, and come back after Halloween. If you neglected to follow this siren song and sell in May, congrats! Stocks just closed May at a new record high, reminding us seasonal myths are as useless as ever.

The original “Sell in May” advice stems from the days when all trading happened in person, on the exchange floor, in bustling business centers of large cities. In May, they purportedly swapped their worsted wool for seersucker, loafers and the coast, leaving trading volumes low and volatility high. So the sage advice for folks who didn’t want their portfolio to wobble unattended was to sell in May, go away, and come back around the St Leger Stakes horserace in September, Britain’s symbolic end to summer. Over time, that sartorial delight morphed into boring data mining, where number crunchers noticed the April 30 – October 31 window was the calendar’s weakest six-month stretch, on average. We aren’t convinced anyone actually sold everything April 30 and bought back in on November 1 year in, year out, but that is what the proverb says to do.

It is all quite silly, as May 2026 demonstrates. Stocks continued their sharp rebound from March’s near-correction over the Iran war and associated high oil fears, with the S&P 500 rising 5.3%.^[i] That is far above May’s average total return since 1926, 0.4%.^[ii] It is also a near-identical repeat of 2025, when stocks jumped in May as they continued rebounding from early-April’s Liberation Day panic. Then, selling in May would have missed a 6.3% return.^[iii] Over last year’s whole Sell in May stretch, the S&P 500 surged 23.6%.^[iv]

Of course, this year’s six-month Sell in May window isn’t concluded. Nothing says it will be equally as robust as 2025’s. Nothing says it will be assuredly positive, despite the strong start. Volatility could resurge. We could get an actual correction (sharp, sentiment-induced drop of -10% to -20%). Given sentiment toward US stocks is much higher than toward developed Europe and Asia, it wouldn’t shock us if US markets underperformed while international led the charge. That might dampen US returns even as global markets do a-ok. But last year’s surge still shows the risks of following seasonal saws. This May’s gains are another reminder of them.

Namely: You risk missing big returns. Last year’s Sell in May window was unusually high, but not unusually positive. Since 1926, returns in that six-month stretch were positive in 73 of 100 years, or 73% of the time.^[v] April 30 – October 31 may be the calendar’s weakest rolling six-month stretch (averaging 4.5%), but “weak” is relative.^[vi] No six-month stretch averages a negative return, and even mild positive gains compound over time. Any positive stretch you miss is a gain that can’t compound over time.

The implicit goal of selling in May is to avoid a negative summer. But given stocks’ long-term returns include all bear markets, corrections and pullbacks along the way, clearly participating in a down stretch needn’t derail your goals. They can be painful to endure, but the subsequent recovery erases them—hence, why the market trends up and to the right over the long haul, with even sharp wiggles shrinking with time and compounding. However, missing gains is a setback. You can’t get them back without taking undue risk like overconcentration or leverage, both of which open the door to magnified declines if you are wrong, setting you even further back and tempting you to take even more risk. It is a vicious hamster wheel.

So don’t get suckered into gimmicks aimed at avoiding short-term volatility, be they seasonal or otherwise. Volatility isn’t a dealbreaker. It is the price we all pay for reaping the long-term returns that get us to our goals. Put that front of mind, and let seasonal myths be the useless trivia they are.