Key Takeaways
- • VOO's top ten holdings make up 37% of the fund and VTI's make up 33%, according to ETF Copilot's analysis of 1,366 US equity ETFs with data as of 10 November 2026, so a broad index core is about as concentrated as the typical equity ETF (35% top-10 share).
- • VOO and VTI overlap heavily: more than 99% of VOO sits inside VTI, and the pair shares 502 holdings, meaning adding VTI to a VOO core adds little diversification.
- • Across all possible fund pairs in the sample, 590 are more than 90% identical by weight, and 73 are more than 99% identical.
- • 453 of the 1,366 funds hold at least one Magnificent 7 stock, with an average Mag 7 weight of 20%; US total-market funds average 24% and covered-call income funds average 22%.
- • Investors should measure top-10 share, two-way overlap, look-through common exposures and drift over time before describing a fund lineup as diversified.
Summary
A research note from the ETF Copilot research team argues that the broad index fund at the core of a portfolio is about as concentrated as the typical US equity ETF, and that the funds surrounding it often hold the same companies. Using each fund's daily holdings disclosures under SEC Rule 6c-11, ETF Copilot computed top-10 share and pairwise overlap across 1,366 US equity ETFs, using data as of 10 November 2026. The note cites S&P Dow Jones Indices, which reported in May 2026 that the ten largest S&P 500 companies made up almost 40% of the index by mid-2025, a level last seen in the mid-1960s.
On concentration, the typical US equity ETF holds 35% of its weight in its ten largest positions and needs 20 holdings to reach half its weight. VTI owns roughly seven times as many companies as VOO (3,432 versus 504 holdings), yet its top ten make up 33% of the fund against 37% for VOO. The range is wide: MSOS, a cannabis fund, has 100% of its weight in its top ten, while RSP, GSEW and SCHA sit at 3%. Of the funds measured, 311 have more than half their weight in the top ten and 323 have less than 20%.
Overlap is the second concern. Across all fund pairs, 590 are more than 90% identical by weight. VOO and VTI share 502 holdings, with more than 99% of VOO inside VTI. QQQ is 93% inside VOO, and SCHD and VIG, both US dividend funds, show asymmetric overlap of 58% and 15%. VTV and VUG share just 2% of their weight. The note stresses that overlap should be measured in both directions because a single percentage can hide cases where one fund sits almost entirely inside another.
Mega-cap technology is a common thread. Of the funds tracked, 453 hold at least one Magnificent 7 stock, with an average Mag 7 weight of 20%. MGK is the highest at 58%, US large-cap growth funds average 34%, VOO is at 33%, US total-market funds average 24%, and options-income (covered-call) funds average 22%. The note suggests that an investor adding a covered-call fund next to a total-market core may be adding exposure to the same Mag 7 companies.
The authors recommend reviewing top-10 share alongside holdings count, checking overlap in both directions, looking through to common sector and Mag 7 exposures across the whole lineup, and re-checking concentration regularly because weights drift with prices. The figures are ETF Copilot's own computations from published holdings and are described as reference data, not investment advice.
On concentration, the typical US equity ETF holds 35% of its weight in its ten largest positions and needs 20 holdings to reach half its weight. VTI owns roughly seven times as many companies as VOO (3,432 versus 504 holdings), yet its top ten make up 33% of the fund against 37% for VOO. The range is wide: MSOS, a cannabis fund, has 100% of its weight in its top ten, while RSP, GSEW and SCHA sit at 3%. Of the funds measured, 311 have more than half their weight in the top ten and 323 have less than 20%.
Overlap is the second concern. Across all fund pairs, 590 are more than 90% identical by weight. VOO and VTI share 502 holdings, with more than 99% of VOO inside VTI. QQQ is 93% inside VOO, and SCHD and VIG, both US dividend funds, show asymmetric overlap of 58% and 15%. VTV and VUG share just 2% of their weight. The note stresses that overlap should be measured in both directions because a single percentage can hide cases where one fund sits almost entirely inside another.
Mega-cap technology is a common thread. Of the funds tracked, 453 hold at least one Magnificent 7 stock, with an average Mag 7 weight of 20%. MGK is the highest at 58%, US large-cap growth funds average 34%, VOO is at 33%, US total-market funds average 24%, and options-income (covered-call) funds average 22%. The note suggests that an investor adding a covered-call fund next to a total-market core may be adding exposure to the same Mag 7 companies.
The authors recommend reviewing top-10 share alongside holdings count, checking overlap in both directions, looking through to common sector and Mag 7 exposures across the whole lineup, and re-checking concentration regularly because weights drift with prices. The figures are ETF Copilot's own computations from published holdings and are described as reference data, not investment advice.
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