Key takeaways
- One global all-cap index fund held 7,500 stocks at 31 July 2026, for a 0.23% ongoing charge. Breadth is solved by the first fund, not the tenth.
- A 50/50 split with an S&P 500 ETF raised the US weight from 61.9% to 81% and NVIDIA's slice from 4.1% to 5.9%. Two funds, a narrower portfolio.
- On ESMA's 2024 averages, active equity funds cost 1.28% a year against 0.22% for passive, so fee drag follows the mix of funds added, not the fund count.
- At the 6.6% real return US equities delivered from 1900 to 2025, £10,000 compounds to roughly £63,900 over 30 years at a 0.22% charge, and £47,400 at 1.28%.
- Over the 20 years to 30 June 2025, 91% of active large-cap US funds trailed the S&P 500, the benchmark a single index fund tracks for 0.07%.
How many funds is too many? The count is the wrong variable
How many funds is too many? The factsheet arithmetic gives an unhelpful answer for anyone hoping for a number: somewhere past the first broad fund, most portfolios stop adding companies and start re-buying the ones they already own, sometimes at a higher price. The count itself barely matters.
Here's the exercise this piece runs. Take real funds with published factsheets, add them one at a time from 1 towards 20, and watch two things: how much of each new fund the portfolio already holds, and what happens to the blended annual charge. Both are measurable to the decimal, and neither behaves the way a fund count suggests.
Start with fund number one. At 31 July 2026, Vanguard's FTSE Global All Cap Index Fund held 7,500 stocks across developed and emerging markets, for a 0.23% ongoing charge. MSCI's ACWI, the other standard global yardstick, held 2,460 large and mid caps across 23 developed and 24 emerging markets at the same 31 July 2026 date, and covers roughly 85% of the world's investable equity value on MSCI's own measure. One purchase, and the breadth question behind how many stocks is diversified is already answered at the scale of whole markets.
So every fund after the first isn't buying diversification. It's buying a tilt, a fee, or both. That's what every later addition has to justify.
The most popular second fund narrows the portfolio
The S&P 500 tracker is where the arithmetic gets uncomfortable. Vanguard's S&P 500 UCITS ETF held 504 stocks at 31 July 2026 and charges 0.07%. Its index is the large-cap end of the one market the global fund already holds most of: the factsheets put the US at 61.9% of the global fund and at 100.0% of the ETF.
Split a portfolio 50/50 between the two and the US weight moves from 61.9% to 81%. NVIDIA moves from 4.1% of the portfolio to 5.9%. The ten largest holdings of the S&P 500 ETF made up 39.1% of its assets, against 22.5% for the global fund. The chart above puts the building blocks side by side: the narrower the fund, the more of it sits in its top ten.
Notice the direction. The portfolio went from one fund to two, and every measure of spread tightened. The fund count rose; diversification fell. That's fund overlap doing its quiet work. On the two objectives Vanguard publishes, the global fund's index spans large, mid-sized and small companies in developed and emerging markets, while the S&P 500 covers large US companies, a subset of that universe. The second fund deepened existing exposure rather than opening new ground. UBS's Global Investment Returns Yearbook adds the context that makes this bite. By end-2025, US equity market concentration stood at its highest level in at least 100 years, and the US made up around 62% of world equity value at the start of 2026. A second fund that doubles up on exactly that corner of the market leans into the most crowded reading in a century of data.
Fund three makes a country bet with passive parts
Now add a FTSE 100 tracker. Vanguard's FTSE 100 Index Unit Trust held 102 stocks at 31 July 2026, charges 0.06%, and carried 49.3% of assets in its top ten, with HSBC alone at 10.5%.
Equal thirds across the three funds put the UK at 34.4% of the portfolio. The global fund weighs the UK at 3.3%, so the three-fund version holds roughly ten times the UK exposure the world market carries, while the US falls to 54%. None of that is wrong. But it's an active country decision wearing index clothing, and the fund count records nothing about it.
Here's the general rule the first three funds demonstrate. Once a portfolio contains a broad fund, every narrower equity fund is a re-weighting of shares it already owns. Duplicate holdings aren't a side effect of multi-fund portfolios; past the first broad fund, they're most of what a new equity fund contains. The question worth asking of fund four, or fourteen, is what it holds that the portfolio doesn't, and the factsheet answers that in a single line.
Fee drag follows what you add, not how many funds you hold
Cost is the second half of the arithmetic, and it's where the count misleads in the opposite direction. ESMA's 2025 market report puts the average ongoing cost of active equity funds in the EU at 1.28% a year for 2024, against 0.22% for passive funds outside ETFs. That's a gap of 1.06 percentage points, paid every year, for the same asset class.
Run the blends across an equal-weighted portfolio and the table looks like this.
| Funds held | What was added | Blended annual charge |
|---|---|---|
| 1 | Global all-cap tracker | 0.23% |
| 2 | S&P 500 ETF | 0.15% |
| 3 | FTSE 100 tracker | 0.12% |
| 5 | 2 average-cost active funds | 0.58% |
| 10 | 5 more average-cost active funds | 0.93% |
| 20 | 17 active funds alongside the 3 trackers | 1.11% |
Read the two halves of that table separately. From 1 fund to 3, the blended charge fell from 0.23% to 0.12%, because each addition was cheaper than the fund before it. From 3 funds to 20, it rose to 1.11%, because the additions were average-priced active funds. The count did nothing. The mix did everything.
Compounding turns that mix into money. US equities returned 6.6% a year in real terms from 1900 to 2025, on the Dimson, Marsh and Staunton series behind the UBS Global Investment Returns Yearbook. £10,000 compounding for 30 years at that return, less a 0.22% charge, reaches roughly £63,900 in today's money. The same £10,000 at a 1.28% charge reaches about £47,400. The £16,500 gap is bigger than the original stake, and the fuller version of that story sits in fund fees compounded over 30 years.
The performance record sharpens the point. Over the 20 years to 30 June 2025, 91% of active large-cap US funds trailed the S&P 500 on S&P's SPIVA scorecard; over the 10 years to the same date, 86% did. ESMA finds the same shape in EU data: over the ten years to end-2024, active equity funds returned 7.6% a year net of ongoing costs against 9.3% for passive peers. Each average-cost active fund added to a list is another draw from a pool where, historically, roughly nine funds in ten have finished behind the index.
The best case for a longer fund list
The strongest objection to everything above is that it prices equity funds against equity funds. A second asset class isn't overlap. A bond fund or a gold holding re-buys nothing in an equity tracker, and the long-run data makes the case for that kind of addition plainly: since 1900, equities and bonds have each lost more than 70% in real terms on several occasions, yet a 60:40 equity and bond blend has never declined by more than 50% in the same series. A portfolio that goes from one fund to four by adding different asset classes has bought something real with every step.
The same yearbook is blunt about which direction equity diversification pays. Across the 32 markets in its world equity index, from 1974 to 2025, investors in the vast majority of markets were better off investing globally rather than domestically once currency risk was hedged, measured by the improvement in their Sharpe ratio, the return earned per unit of risk. The broad first fund is the best-evidenced purchase in the whole stack; the argument here is only about what comes after it.
The cost argument can also invert. The three-tracker blend above charges 0.12%, less than the 0.23% single global fund, because narrow index funds price below all-cap ones. A critic of the one-fund answer can fairly say the cheapest broad exposure in the table was assembled from parts, not bought whole. The price of assembly is that the rebalancing work, and the country weights, become the holder's own responsibility.
Active additions have their seasons too. In the first half of 2025, 54% of active large-cap US funds underperformed the S&P 500, which SPIVA describes as the industry tracking towards its best year since 2022. A short fund list holding a few high-conviction managers is a bet that the selection lands in the minority. The record above prices that bet; it doesn't forbid it.
What this arithmetic cannot tell you
Every number here has edges. The 1.28% active average is an EU-wide figure for 2024; a given list might hold active funds priced far below it, and ESMA notes its figures exclude distribution costs, which its earlier analysis put at 48% of total UCITS costs. The headline SPIVA rates are US large-cap data: in the same mid-year 2025 scorecard, only 22% of small-cap funds trailed their benchmark over the first half of the year, so the odds shift with the category and the window. The 6.6% real return is US history from 1900 to 2025, not a forecast, and it was earned by the market that now sits at a 100-year concentration high.
The factsheet weights are one month's snapshot, dated 31 July 2026, and they drift. The equal-weight scenarios are illustrations, not reconstructions of any real portfolio; a fund added as a small position moves the blend far less than an even split does. And overlap is measured here with a coarse ruler, country and top-ten weights, when two funds can share every holding and still weight them differently. MSCI's 85% coverage figure counts large and mid caps only; the small-cap tail sits outside ACWI, which is one reason the all-cap fund holds roughly three times as many names. The sample, in every case, is the past.
What would change the answer
If US market concentration unwinds from its end-2025 extreme, the cost of holding overlapping funds that double the same ten companies shrinks with it, and the 50/50 example above reads as a milder tilt than it does today.
If fee gaps keep closing, the drag half weakens. ESMA measured retail equity fund ongoing costs declining by 8% between 2020 and 2024; an active average that converged towards the passive one would take most of the fee argument with it.
And if the funds being added are genuinely non-overlapping, other asset classes and missing geographies at passive prices, the count can rise towards 20 with no fee drag and no re-buying at all. That's the point of running the arithmetic instead of counting holdings lines: the number of funds was never the variable that mattered. The two figures that were, the blended ongoing charge and the share of the portfolio in its ten biggest positions, both sit on public factsheets, and LedgerTouch computes both continuously across whatever mix of funds a portfolio holds.