S&P 500: ten companies account for 41% of the index

Buying a fund that tracks the S&P 500 means, in principle, buying a slice of 500 American companies. In practice, the allocation is very uneven. According to Citadel Securities data as of October 6, 2026, charted by The Kobeissi Letter, 41 cents of every dollar invested in the index go to the ten largest companies by market capitalization. These figures are reported by the website Journal du Coin in an article published on October 11, 2026.

What a dollar invested really contains

The published breakdown is as follows, again according to The Kobeissi Letter's chart based on Citadel Securities (reading as of October 6, 2026, amounts rounded to the cent). Nvidia alone receives 8 cents. Next come Apple (7 cents), Microsoft and Alphabet (6 cents each), then Amazon (4 cents). Broadcom, Meta, Tesla, Micron and AMD share the next 10 cents.

Further down the ranking, the companies in eleventh to twentieth place receive 10 cents combined. The top twenty companies therefore absorb 51 cents, more than half of the dollar. The next eighty receive 26. The 402 smallest share 23 cents, that is, four less than the top four holdings combined (Nvidia, Apple, Microsoft and Alphabet, 27 cents in total).

Journal du Coin also notes that four chipmakers, Nvidia, Broadcom, Micron and AMD, together account for 14 cents. The website draws a conclusion from this: buying “the American market” today amounts, in its view, to taking a large position on artificial intelligence. This is the source's interpretation, not data published by Citadel Securities.

A level above the peaks of 1973 and 2000

To put this figure in historical context, Journal du Coin draws on series from Goldman Sachs Asset Management. According to these, the top ten stocks accounted for about 22% of the index in 1973, in the era of the “Nifty Fifty,” and 27% at the peak of the dot-com bubble in 2000.

The current level, however, depends on the calculation method. Over the summer of 2026, the readings cited by the source ranged between 36.5% and 41%. The 41% figure is the one from Citadel Securities as of October 6, 2026.

The phenomenon is also visible at the very top of the ranking. The top three holdings, Nvidia, Apple and Microsoft, together account for 21% of the index, a record noted by the website Benzinga. By comparison, the source states that in the mid-1980s, the leading trio of IBM, AT&T and Exxon topped out at 13.4%.

How we got here

The explanation put forward by Journal du Coin lies in the very construction of the index. The S&P 500 weights each company according to its stock market value. The more a stock's price rises, the more weight it carries in the index, and the more of it the funds tracking the index must buy. According to the source, this mechanism is self-reinforcing during a period of successive records on Wall Street.

This point is worth emphasizing for investors who choose an index ETF thinking they are diversifying: the product does not spread their money equally across 500 companies. It follows market weights, which are currently dominated by a handful of very large companies.

How it is being interpreted

The source refrains from a clear-cut conclusion and itself describes the answer as “nuanced.” It recalls that the two best-known concentration peaks, 1973 and 2000, preceded long bear markets, while specifying that two examples do not make a rule and that a concentrated index is not doomed to fall. The observation it highlights is simpler: the index's performance depends more on the health of a small number of companies. A sharp decline in Nvidia, for example, would weigh on an S&P 500 ETF regardless of how the bottom 402 holdings perform.

Journal du Coin also mentions the existence of a so-called equal-weight version of the index, in which each company has the same weight. According to the source, it corrects this bias, at the cost of much lower exposure to the tech giants. This mention does not constitute a recommendation: the two approaches follow different logics, and the source does not compare their performance.

Several uncertainties remain. The figures come from a third-party chart based on Citadel Securities data, rounded to the cent. Concentration measures vary depending on the method used, as shown by the summer range between 36.5% and 41%. Finally, weights change with prices: the October 6, 2026 reading describes the situation on a given date, not a lasting state.

And for a portfolio in Switzerland?

The source does not address the Swiss case. The question may nonetheless arise for any saver in Switzerland who holds exposure to the S&P 500, directly or through a fund: what share of their portfolio really depends on about ten American companies? And if other index investments are also weighted by market capitalization, do they not reinforce that same exposure rather than dilute it?

These questions do not call for a single answer. Above all, they invite a look at a product's actual composition, not just the number of securities it holds. This article does not constitute investment advice.

Source: Journal du Coin, “S&P 500: 10 companies account for 41% of the index,” October 11, 2026