The takeaway
Vanguard Mega Cap Index Fund ETF Shares shows a moderate seasonal pattern over 10 years of data — strongest in July (+3.1%) and softest in February (−0.9%).
Right now
In July, the fund has risen 90% of years, averaging +3.1%, about +0.9 pts better than the S&P 500.
The full picture
Vanguard Mega Cap Index Fund ETF Shares's most dependable month has been July, higher in 9 of 10 years; February has been its least reliable, up just 40% of the time.
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Month by month
The fund's clearest edge over the S&P 500 lands in January (+1.8 pts); it has trailed the market most in March (−1.3 pts).
“vs S&P” is Vanguard Mega Cap Index Fund ETF Shares’s average for a month minus the S&P 500’s average for that same month — isolating Vanguard Mega Cap 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
Dependability is the through-line here. July stands out, higher in 9 of 10 Julys, but it heads a clutch of months that pull the year reliably upward.
Its average (+3.1%) and median (+3.0%) land within a hair of each other — the tell of steady, year-after-year gains rather than one outlier doing the work. It is also the calendar's calmest month, its returns swinging least from year to year (a 2.2% spread), and even its worst July in 10 years lost only 0.0% — the gentlest downside anywhere on its calendar. Crucially, the gain is the fund's own rather than a rising tide's: July has cleared the S&P 500 by +0.9 points above the index. That consistency sets it apart from the field, where the average stock manages July only about 61% of the time.
The strength clusters rather than stands alone — March–August forms a firm stretch that carries much of the year. The weaker half of the year is plainer: February has been the soft spot — the weakest of 2 months that average a loss (−0.9%), and the edge isn't year-round — the fund has trailed the S&P 500 in March, September, and December. Its roughest month on record was a −15.5% March in 2020 — a reminder of how hard even a seasonal name can fall.
At its steadiest, July strung together 8 straight positive years. Reassuringly, the tendency has held its shape: the recent five years still track the years behind them.
The takeaway is less about when to buy than what to expect: July aside, the fund's months offer little reliable tilt.
Short answers on the fund's best month (July), its worst (February), and whether it really trades seasonally.
Yes, to a moderate degree. Since 2016 its best month (July, +3.1%) has run well ahead of its worst (February, −0.9%) — the heatmap above shows how steady that gap has been year to year.
July has been the strongest, averaging +3.1% and closing higher in 9 of 10 years since 2016.
It's the weakest, averaging −0.9% — 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