The takeaway
Vanguard Total Bond Market Index Fund ETF Shares shows a slight seasonal lean over 10 years of data — strongest in July (+0.8%) and softest in September (−0.6%).
Right now
In July, the fund has risen 90% of years, averaging +0.8%, roughly 1.3 pts behind the S&P 500.
The full picture
Vanguard Total Bond Market Index Fund ETF Shares's most dependable month has been July, 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 January (+0.7 pts); it has trailed the market most in April (−1.9 pts).
“vs S&P” is Vanguard Total Bond Market Index Fund ETF Shares’s average for a month minus the S&P 500’s average for that same month — isolating Vanguard Total Bond Market Index Fund ETF Shares’s own seasonal edge from broad market drift.
Reality check
Over the last 5 years, July has closed higher 80% of the time versus 90% across the last 10 years — the pattern is holding.
Figures are the typical (median) July 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
This is a fund you can almost set a calendar by, and July is the anchor — it has closed higher in 9 of 10 Julys, the steadiest beat on its year.
The strength looks broad-based rather than freakish: its average (+0.8%) and median (+0.5%) sit close together, so no single blow-out year is flattering the figure. Few months are steadier: July's returns vary by just 0.9% year to year, and even its worst July in 10 years lost only 0.2% — the gentlest downside anywhere on its calendar. Few peers keep such company in July — the typical stock clears it just 61% of the time.
July anchors a run, too: the March-through-July window has been the fund's reliable season. The weaker half of the year is plainer: September has been the soft spot — the weakest of 2 months that average a loss (−0.6%), and the edge isn't year-round — the fund has trailed the S&P 500 in April, October, and November.
One run worth flagging just ended: a 9-year streak of positive Julys was snapped by a −0.2% close in 2025. Reassuringly, the tendency has held its shape: the recent five years still track the years behind them.
For a fund this dependable in July, the sharper question is the rest of the year — outside its strong stretch, the calendar gives far less to lean on.
Short answers on the fund's best month (July), its worst (September), and whether it really trades seasonally.
Only mildly. The fund's months are fairly even — July is the firmest (+0.8%) and September the softest (−0.6%), a narrow spread that points to weak seasonality rather than a strong calendar effect.
July has been the strongest, averaging +0.8% and closing higher in 9 of 10 years since 2016.
It's the weakest, averaging −0.6% — 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.
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