ETF Overlap: How Much Mag 7 Is in Your Portfolio?

ETF overlap is when two or more of your funds own the same companies, so your real exposure to those companies is larger than any single line in your broker account shows. In 2026 the overlap that matters is the Magnificent 7. On 31 August, seven American companies made up 23.6% of the MSCI World, the index behind the most popular ETF in Europe. Put an S&P 500 ETF next to it, as many DEGIRO investors do, and those seven stocks can come close to 30% of your money.

In August the European Central Bank put a number on it. In a post on the ECB Blog, five of its economists wrote that euro area households hold about €440 billion of US technology stocks, mostly through funds and ETFs, "without necessarily being aware of the associated concentration risk." The same post said a correction of current valuations is likely.

This guide shows how concentrated the big world ETFs are today, how to calculate your own look-through exposure in five steps, and what your options are if the number surprises you.

---

What is ETF overlap?

ETF overlap is the percentage of holdings that two funds share. Look-through exposure is what you get when you open every fund in your portfolio, add up the companies inside, and count your direct shares too. Your broker shows positions. Look-through shows owners.

The two numbers can be very different. An MSCI World ETF and an S&P 500 ETF look like two separate products with two names and two tickers. Inside, about 72% of the MSCI World is US large and mid-cap stocks, and nearly all of them are also in the S&P 500. The second fund adds very few new companies. It adds more weight to the ones you already hold.

That is fine if you planned it. Most people didn't.

How concentrated is the MSCI World in 2026?

The MSCI World tracks 1,280 companies in 23 developed countries. Here are the ten largest, from MSCI's own factsheet dated 31 August 2026:

Ten companies out of 1,280 hold more than a quarter of the index. Information technology alone is 29.81%. The United States is 72.14%.

Now compare the Magnificent 7 with the rest of the planet. Nvidia, Apple, Microsoft, Amazon, both Alphabet share classes, Meta and Tesla add up to 23.6%. The 22 countries that are not the US add up to 27.9%. Seven American companies weigh almost as much as Japan, the UK, Canada, France, Germany, Switzerland, the Netherlands and every other developed market combined.

Nvidia on its own (5.56%) is close to all Japanese stocks in the index (5.78%), and bigger than the whole UK (3.53%). The name "World" describes where the index looks. It doesn't describe where the money goes.

MSCI World vs FTSE All-World vs S&P 500

Most European ETF investors hold one of three indexes as their core. Here is how they compare on concentration:

MSCI World: MSCI factsheet, 31 August 2026. FTSE All-World: Vanguard FTSE All-World UCITS ETF factsheet, 31 August 2026. S&P 500 figures are approximate for late summer 2026.

The FTSE All-World is a bit less concentrated because it includes emerging markets: Taiwan (3.3%), China (2.7%) and Korea (2.5%) take weight away from the US. Even so, about one euro in five still goes to the same seven companies. Switching from IWDA to VWCE changes the dose. It doesn't change the medicine.

The MSCI World and S&P 500 overlap: the classic double-up

A pattern you see again and again on r/eupersonalfinance and in DEGIRO accounts is a world ETF plus "a bit extra" in the S&P 500 or the Nasdaq-100. It feels like diversification. Two funds, two indexes.

Do the math on a 50/50 split between an MSCI World ETF and an S&P 500 ETF. Half your money is 72.1% US, the other half is 100% US. Your total US share is about 86%. The Magnificent 7 come to roughly 28%, and Nvidia alone to about 6.6%.

A Nasdaq-100 ETF pushes it further, because that index is even more tilted toward the same mega caps. Every extra US growth fund you add on top of a world fund raises the weight of companies you already own.

What your broker shows vs what you actually own

Take a realistic DEGIRO portfolio of €25,000:

• €14,000 in an MSCI World ETF (IWDA)
• €8,000 in an S&P 500 ETF (CSPX)
• €1,500 in Nvidia shares, bought as a "small bet on AI"
• €1,500 in ASML shares

The broker list shows four lines. Nvidia is €1,500, or 6% of the account. That looks like a modest satellite position.

Now look through the funds. Nvidia is 5.56% of the MSCI World ETF and about 7.7% of the S&P 500 ETF:

The Nvidia line is €14,000 × 5.56% + €8,000 × 7.7% + €1,500 in direct shares. The "small bet" is almost twice the size the owner thinks. Nearly 30% of the portfolio rides on seven stocks, and close to 80% on one country. (ASML also sits inside the MSCI World, at a weight too small to change the result.)

There is a currency side too. Those €19,600 in US stocks earn in dollars, even if the ETF is listed in euros on Xetra or Euronext. A euro-listed share class doesn't remove the dollar exposure. Our post on how EUR/USD moves eat into your returns shows what that did to European portfolios this year.

How to calculate your look-through exposure in 5 steps

You don't need special software for this. You need your positions, the factsheets, and twenty minutes.

1. List every position with its current value, across all brokers. In DEGIRO, export your portfolio as a CSV. If you also use Trade Republic or a bank account, add those positions. A tracker like Zune.Money imports your DEGIRO transactions CSV and shows every holding with its weight in one list, which saves you this step every quarter.
2. Open the factsheet of each ETF. Every issuer publishes a monthly PDF with the top 10 holdings and the country split. Use the same month for all your funds, or the numbers won't add up cleanly.
3. Multiply the ETF value by each company's weight. €14,000 × 5.56% = €778 of Nvidia. Do this for the five largest names and for the US share. The long tail rarely changes the picture.
4. Add your direct shares of the same companies. This is the step most people skip, and the one where overlap hides best.
5. Divide by your total portfolio value, and write the result down. Put it next to a limit you chose in advance, like "no single company above 10%" or "US below 70%". A number without a limit next to it is trivia.

Repeat it once a quarter, and every time you add a new fund or buy a stock that already lives inside your ETFs. For the wider view of how far your allocation has drifted, see our guide to rebalancing at record highs.

Is concentration actually a problem?

Honest answer: not automatically.

A market-cap index owns companies in proportion to their market value. When Nvidia weighs 5.56%, it is because investors as a group value it that way, and these companies earn real profits. Concentration has also been high before and lasted for years. Anyone who sold their world ETF in 2023 to "escape" big tech missed a large part of the gains since then.

But there are reasons to watch it. The ECB blog notes that Nvidia's share price rose about 20-fold since 2022 and that US valuations are near levels last seen in the dot-com era. The MSCI World trades at 23.2 times trailing earnings. Its worst drawdown, from October 2007 to March 2009, was 57.5%, and in 2022 it fell 17.7% in one year. When the leaders of a concentrated index fall, they take a big part of the index with them, because they are a big part of the index.

The right question is not whether 23.6% is too much in general. It is whether the number in your own portfolio is the number you chose. In the example above, the owner chose 6% Nvidia and got 11.6%. That gap is the real problem.

This is not investment advice. What follows are options, not recommendations.

What to do if your ETF overlap is too high

Drop the double. If you hold a world ETF, an S&P 500 or Nasdaq-100 ETF on top adds weight, not companies. Many investors stop new contributions to the second fund and let the world fund do the job.

Steer new money instead of selling. Selling triggers capital gains tax in most European countries. Directing your monthly contributions to the under-weighted part of your plan moves the allocation without a tax event. It is slower, and for most people it is the better trade-off.

Add what is under-represented. Europe is a small slice of the MSCI World, and emerging markets and small caps are not in it at all. A separate fund for any of them lowers the US share. We looked at the case for Europe in European stocks vs US: time to rotate?.

Look at equal-weight or ex-USA versions. Several issuers offer MSCI World variants that weight every company the same, or leave the US out. Check the costs first. Equal-weight funds have higher fees and more turnover.

Set your own cap. Pick one or two rules and write them down. For example: no single company above 10% look-through, US below 75%. The exact numbers matter less than having them before the market tests you.

Do nothing, on purpose. Holding a cap-weighted world ETF and accepting its concentration is a valid choice. The difference is that you now know what you hold.

Tax rules vary by country, so check with a tax advisor before you sell anything to rebalance.

Keep the number visible

Concentration creeps. You don't decide to own 11% Nvidia. You buy a world ETF in 2022, an S&P 500 ETF in 2024, a few Nvidia shares in 2025, and the market does the rest. Each decision made sense on its own. The total is something nobody chose.

The fix is to look at the total regularly. Import your DEGIRO CSV into Zune.Money and you see every position and its weight in one dashboard, with allocation by sector and country next to it. The five-step check then takes minutes instead of an evening. The free plan covers the import and the holdings list.