The takeaway
Vanguard Extended Duration Treasury Index Fund ETF Shares shows a moderate seasonal pattern over 10 years of data — strongest in November (+2.1%) and softest in September (−2.6%).
Right now
In July, the fund has risen 60% of years, averaging +1.3%, roughly 0.9 pts behind the S&P 500.
The full picture
Vanguard Extended Duration Treasury Index Fund ETF Shares's most dependable month has been November, higher in 9 of 10 years; September has been its least reliable, up just 20% of the time.
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Month by month
The fund's clearest edge over the S&P 500 lands in June (+2.1 pts); it has trailed the market most in October (−4.7 pts).
“vs S&P” is Vanguard Extended Duration Treasury Index Fund ETF Shares’s average for a month minus the S&P 500’s average for that same month — isolating Vanguard Extended Duration Treasury Index Fund ETF Shares’s own seasonal edge from broad market drift.
Reality check
Over the last 5 years, November has closed higher 100% of the time versus 90% across the last 10 years — the pattern is strengthening.
Figures are the typical (median) November return and how often it rose — the last 5 years versus the last 10(the heatmap’s default window). This verdict stays anchored to that 10-year window even if you zoom the chart, so it never disagrees with the badges above.
In plain English
Strip the year back and a single month does the heavy lifting: November, up in 9 of 10 Novembers while the other eleven tend to blur together.
Its average (+2.1%) and median (+1.6%) land within a hair of each other — the tell of steady, year-after-year gains rather than one outlier doing the work. Set against the S&P 500, mind, November is close to a wash — the gain mirrors the market more than it beats it. That consistency sets it apart from the field, where the average stock manages November only about 62% of the time.
A few other months pull their weight: March, June, and July have also closed higher more often than not. The weaker half of the year is plainer: September has been the soft spot — the weakest of 4 months that average a loss (−2.6%), and the edge isn't year-round — the fund has trailed the S&P 500 in October, April, and September. Its roughest month on record was a −13.1% April in 2022 — a reminder of how hard even a seasonal name can fall.
November has now closed higher 9 years running. If anything it has sharpened recently — the last five Novembers run ahead of the earlier years.
The takeaway is less about when to buy than what to expect: November aside, the fund's months offer little reliable tilt.
Short answers on the fund's best month (November), its worst (September), and whether it really trades seasonally.
Yes, to a moderate degree. Since 2016 its best month (November, +2.1%) has run well ahead of its worst (September, −2.6%) — the heatmap above shows how steady that gap has been year to year.
November has been the strongest, averaging +2.1% and closing higher in 9 of 10 years since 2016.
It's the weakest, averaging −2.6% — historically a soft spot, though it still varies from year to year.
Explore
These names have the strongest July track records on record — a starting point for comparison.
Before you trade