'Sell in May and go away' is an old market saying that resurfaces every year. The full version runs: 'Sell in May and go away, and come back on St Leger's Day', a reference to the Doncaster thoroughbred race held each September, which traditionally marked the end of the English social season.
The saying dates to an era when City stockbrokers downed tools for summer, meaning less capital was being put to work and markets drifted relatively aimlessly. The adage has survived because UK equity data gives it enough support to keep it plausible.
Across all of the Investment Association and Association of Investment Companies sectors, data for the past 10 years shows that the average return between May and September has been higher than from September to April in almost every open-ended sector. The exceptions were UK equity and commodity funds, as the table below shows.
IA sectors where ‘Sell in May’ worked the least in the past decade
| Name | 10yr average return May-September | 10yr average return September-April | Delta |
| IA India/Indian Subcontinent | 9.6% | 0.1% | 9.5 |
| IA Healthcare | 7.3% | 0.8% | 6.5 |
| IA Global EM Bonds - Hard Currency | 5.4% | -1.0% | 6.4 |
| IA EUR Government Bond | 3.6% | -2.2% | 5.7 |
| IA EUR Mixed Bond | 3.7% | -1.9% | 5.6 |
| IA UK Index Linked Gilts | 2.4% | -2.5% | 5.0 |
| IA Global EM Bonds - Blended | 4.7% | -0.3% | 4.9 |
| IA EUR High Yield Bond | 5.0% | 0.1% | 4.9 |
| IA USD Corporate Bond | 4.2% | -0.7% | 4.9 |
| IA EUR Corporate Bond | 3.7% | -1.2% | 4.8 |
| IA Japan | 7.5% | 2.7% | 4.8 |
| IA North American Smaller Companies | 8.8% | 4.2% | 4.6 |
| IA Global EM Bonds - Local Currency | 4.0% | -0.3% | 4.3 |
| IA Financials and Financial Innovation | 7.9% | 3.7% | 4.2 |
| IA USD Mixed Bond | 3.6% | -0.6% | 4.2 |
| IA Global Corporate Bond | 3.8% | -0.3% | 4.2 |
Source: FinXL
IA sectors where ‘Sell in May’ worked the most in the past decade
| Name | 10yr average return May-September | 10yr average return September-April | Delta |
| IA UK Equity Income | 2.6% | 5.1% | -2.5 |
| IA Commodity/Natural Resources | 5.6% | 7.8% | -2.2 |
| IA UK All Companies | 3.2% | 4.4% | -1.2 |
| IA UK Direct Property | 0.4% | 1.1% | -0.7 |
| IA Standard Money Market | 0.7% | 1.2% | -0.5 |
| IA Short Term Money Market | 0.6% | 1.1% | -0.5 |
| IA Targeted Absolute Return | 1.4% | 1.8% | -0.4 |
| IA Europe Including UK | 4.6% | 4.7% | 0.0 |
| IA UK Smaller Companies | 3.5% | 3.4% | 0.0 |
| IA Europe Excluding UK | 5.3% | 4.8% | 0.5 |
| IA Global Equity Income | 5.6% | 4.7% | 0.9 |
| IA Mixed Investment 20-60% Shares | 3.0% | 2.0% | 1.0 |
| IA Asia Pacific Excluding Japan | 6.0% | 4.9% | 1.1 |
| IA Sterling Strategic Bond | 2.2% | 1.0% | 1.1 |
| IA Sterling Corporate Bond | 1.8% | 0.6% | 1.2 |
| IA Mixed Investment 0-35% Shares | 2.2% | 1.0% | 1.2 |
Source: FinXL
But this doesn’t tell the whole picture, according to Jason Hollands, managing director of Bestinvest by Evelyn Partners.
"While UK equities have shown a tendency towards summer softness this is far from a reliable or consistent pattern and, once dividends are factored in, the case for selling ahead of the summer becomes even weaker," he said.
Peer groups that have tended to perform particularly well over the summer are India and Japan, as well as healthcare and financials. Meanwhile, IA Global and IA North America funds delivered positive May-to-September average returns in all 10 of the summers studied; the average fund in the IA Technology and IA Healthcare managed this in nine of 10.
Data from Rathbones shows that, overall, investors who sold in May and returned in September would have been around 8% worse off over the past decade, based on returns from the S&P 500.
This could be even more critical now, with US president Donald Trump tending to stir up markets in the early portion of the year before things calm down over the summer,
IG analysis found that the S&P 500 has returned an average 9.5% between May and October during Trump's presidential years against 1.3% during non-Trump years over the past two decades, chief market analyst Chris Beauchamp attributing this to policy-driven volatility.
"While investors have had to ride out serious market sell-offs, rebounds have been strong and relief moments for investors have led to rapid significant gains across US equities, in particular during Trump's time in the Oval Office."
An example of this was last year, where tariff shocks from Trump’s ‘Liberation Day’ sparked a major sell-off that subsequently recovered in May and June.
A similar pattern is visible among investment trusts too. IT Technology's summer average across the decade tracks its open-ended equivalent but with wider spreads. IT Commodities & Natural Resources shows an even sharper seasonal reversal than open-ended funds.
IT sectors where ‘Sell in May’ worked the least in the past decade
| Name | 10yr average return May-September | 10yr average return September-April | Delta |
| IT India/Indian Subcontinent | 10.6% | 0.7% | 9.9 |
| IT Country Specialist | 8.2% | -1.0% | 9.2 |
| IT Biotechnology & Healthcare | 8.1% | 0.6% | 7.6 |
| IT Property - UK Residential | 3.1% | -3.4% | 6.5 |
| IT Property Securities | 5.5% | -0.2% | 5.7 |
| IT Japanese Smaller Companies | 7.7% | 2.6% | 5.1 |
| IT Growth Capital | 2.7% | -2.1% | 4.9 |
| IT Japan | 8.2% | 3.6% | 4.6 |
| IT Leasing | 4.6% | 0.4% | 4.2 |
| IT Debt - Structured Finance | 6.1% | 2.9% | 3.2 |
| IT Renewable Energy Infrastructure | 2.7% | -0.3% | 3.0 |
| IT Debt - Direct Lending | 2.8% | 0.0% | 2.8 |
| IT VCT AIM Quoted | 3.0% | 0.4% | 2.6 |
| IT Property - Europe | 1.9% | -0.7% | 2.6 |
| IT Asia Pacific Smaller Companies | 6.6% | 4.3% | 2.4 |
| IT Global | 6.2% | 4.1% | 2.1 |
Source: FinXL
IT sectors where ‘Sell in May’ worked the most in the past decade
| Name | 10yr average return May-September | 10yr average return September-April | Delta |
| IT UK Equity & Bond Income | 1.4% | 7.1% | -5.6 |
| IT UK All Companies | 1.7% | 6.3% | -4.5 |
| IT UK Equity Income | 1.9% | 6.2% | -4.2 |
| IT China/Greater China | 4.4% | 6.8% | -2.4 |
| IT Commodities & Natural Resources | 8.3% | 10.3% | -2.1 |
| IT Financials & Financial Innovation | 4.0% | 5.2% | -1.2 |
| IT Property - UK Commercial | 1.1% | 2.3% | -1.1 |
| IT Hedge Funds | 3.8% | 4.7% | -0.9 |
| IT Global Equity Income | 4.8% | 5.5% | -0.7 |
| IT Property - UK Logistics | 3.8% | 4.5% | -0.7 |
| IT Latin America | 4.5% | 5.1% | -0.6 |
| IT Asia Pacific Equity Income | 5.8% | 6.3% | -0.4 |
| IT Flexible Investment | 2.9% | 3.1% | -0.2 |
| IT Private Equity | 4.8% | 4.9% | -0.2 |
| IT Infrastructure Securities | 8.3% | 8.4% | -0.1 |
| IT Europe | 5.0% | 5.0% | 0.0 |