The takeaway
Dimensional ETF Trust shows a slight seasonal lean over 3 years of data — strongest in May (+0.5%) and softest in September (+0.3%).
Right now
In July, the fund has risen 100% of years, averaging +0.4%, roughly 1.7 pts behind the S&P 500.
The full picture
Dimensional ETF Trust's most dependable month has been May, higher in 2 of 2 years; September has been its least reliable, up just 100% of the time.
| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Win rate % | ||||||||||||
| Median return % | ||||||||||||
| 2025 | ||||||||||||
| 2024 | ||||||||||||
| 2023 | — | — | — | — | — | — | — | — |
Month by month
The fund's clearest edge over the S&P 500 lands in January (+0.6 pts); it has trailed the market most in November (−1.9 pts).
“vs S&P” is Dimensional ETF Trust’s average for a month minus the S&P 500’s average for that same month — isolating Dimensional ETF Trust’s own seasonal edge from broad market drift.
Reality check
Not enough recent May history to say whether the pattern still holds.
Figures are the typical (median) May return and how often it rose — the last 2 years versus the last 3(the heatmap’s default window). This verdict stays anchored to that 3-year window even if you zoom the chart, so it never disagrees with the badges above.
In plain English
This is a fund you can almost set a calendar by, and May is the anchor — it has closed higher in all 2 Mays, the steadiest beat on its year.
The strength looks broad-based rather than freakish: its average (+0.5%) and median (+0.5%) sit close together, so no single blow-out year is flattering the figure. Few months are steadier: May's returns vary by just 0.0% year to year, and even its worst May in 3 years lost only 0.5% — the gentlest downside anywhere on its calendar. Set against the S&P 500, mind, May is close to a wash — the gain mirrors the market more than it beats it. Few peers keep such company in May — the typical stock clears it just 55% of the time.
The lift is near-universal — strength runs through almost every month of the year, not one window. The weaker half of the year is plainer: September is the year's quietest corner, essentially flat on average, and the edge isn't year-round — the fund has trailed the S&P 500 in November, July, and April.
For a fund this dependable in May, the sharper question is the rest of the year — outside its strong stretch, the calendar gives far less to lean on. With a short 3-year record, the signal is best held loosely.
Short answers on the fund's best month (May), its worst (September), and whether it really trades seasonally.
Only mildly. The fund's months are fairly even — May is the firmest (+0.5%) and September the softest (+0.3%), a narrow spread that points to weak seasonality rather than a strong calendar effect.
May has been the strongest, averaging +0.5% and closing higher in all 2 years on record since 2023.
It's the weakest month, but it has still averaged a small gain (+0.3%) — quiet rather than genuinely bad.
Explore
These names have the strongest July track records on record — a starting point for comparison.
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