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What does "sell in May and go away" mean?

In one line: "Sell in May and go away" is an old market saying suggesting stocks tend to do worse from May to October than from November to April.

Trading glossary · Updated 2026-10-21

What it means

The idea: sell your stocks in May, sit out the summer, and buy back in the fall. The thought is that stocks tend to do worse in the warmer months.

Some people call the flip side the "Halloween effect": buy back around the end of October.

Where it comes from

It's an old British saying. A longer version is "Sell in May and go away, and come on back on St Leger's Day." The St Leger is a horse race held in England each September. The idea was that wealthy traders left the city for the summer, so markets were quieter.

What the history shows

Some studies of past data found that, on average, stocks gained less from May to October than from November to April, in many countries. That's the "seasonal" effect.

But there are big catches:

• Average isn't every year. Many summers had strong gains. Sitting out would have missed them.
• The gap varies a lot, and some researchers argue it's too small or unreliable to act on.
• Costs add up. Selling and buying back has costs and, in many accounts, taxes.

The real lesson

Calendars can shape markets a little. Summer often has thinner trading, for example. It's fine to know about it.

The trap inside it

The trap is treating a pattern from the past as a rule for the future. A saying that worked "on average" can fail for years at a time.

It also invites Confirmation bias: you remember the summers that fit and forget the ones that didn't.

A simple example

Picture two summers.

• Year 1: stocks fall 8% from May to October. "Sell in May" looks clever.
• Year 2: stocks rise 10% over the same months. "Sell in May" missed it all.

On average the rule may look fine. In any single year, it's a coin you can't see. Illustration only, not real index data.

A better approach

If you're curious whether a seasonal idea holds up, test it yourself on past charts and log the results. See how to backtest a trading strategy. Then decide with your plan, not a rhyme. Our how to write a trading plan guide shows how.

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