MSCI World vs S&P 500: how stock market indices work for investors

• MSCI World: 1,248 companies from 23 developed countries as of October 30, 2026, 72.8% of them in the US, and no emerging markets at all.
• S&P 500: the 500 largest US companies, about 80% of the US stock market; the top ten make up 37.6% of the index.
• CW8: an Amundi ETF that replicates the MSCI World, eligible for the French PEA through synthetic replication, with 0.38% ongoing charges a year.
• Returns: 8.98% a year for the MSCI World since the end of 1987, dividends reinvested and in dollars, with a 57% fall in 2008-2009.

“Invest in the MSCI World”, “buy the S&P 500”: these phrases come up in every piece of advice for new investors, so often that people forget what they mean. An index is not an investment; it is a list of companies and a calculation rule. What you buy is a fund, usually an ETF, that reproduces the list. And two indices whose names suggest “the world” do not hold the same things at all.

This guide explains what a stock market index is, what the MSCI World, the S&P 500, the MSCI ACWI, the emerging markets index, the Nasdaq-100 and the main European indices contain, what they have returned and lost in the past, and how to hold them through an ETF such as CW8, including in a French PEA. The figures come from the official factsheets of MSCI (October 30, 2026) and S&P Dow Jones Indices (July 31, 2026).

What is a stock market index?

A stock market index is a number that sums up how a group of shares is moving. Its provider, such as MSCI, S&P Dow Jones Indices or Euronext, picks the companies under public rules (country, size, liquidity, sometimes profits), then calculates the value of the basket throughout the trading day. When people say “the S&P 500 rose 2%”, they mean the combined value of its 500 companies went up 2%.

Most major indices are weighted by market capitalization: the more a company is worth on the stock market, the more it counts. Apple, worth more than $5 trillion at the end of October 2026, therefore makes up 5.65% of the MSCI World, while the smallest of the 1,248 companies weighs a tiny fraction of that. This rule automatically increases the weight of companies that rise, without anyone having to decide what to buy.

Price index or total return index

The same index comes in several versions. The “price” version, the one quoted in the news, follows share prices only. The “total return” version adds the dividends paid, as if they were immediately reinvested in shares. Over long periods the gap is large: the second one measures what an investor would really have earned, and it is the one accumulating ETFs track. MSCI publishes a “net” version, after withholding tax on dividends, and a “gross” version, before it.

The MSCI World: 1,248 companies from 23 developed countries

The MSCI World, launched in 1986 by the US company MSCI, brings together the large and mid caps of 23 developed countries: the United States, Canada, Japan, Australia, New Zealand, Hong Kong, Singapore, Israel and fifteen European countries, France included. It covers about 85% of the free-float value of each market. As of October 30, 2026, it holds 1,248 companies worth nearly $90 trillion in total, according to MSCI's official factsheet.

Its name is misleading on one point: the MSCI World is not the world. It holds no emerging markets: not China, India, Taiwan or Brazil. And it is very American:

The top ten companies alone make up 26.58% of the index: Apple (5.65%), Nvidia (5.25%), Microsoft (4.11%), then Amazon, Alphabet (with its two share classes), Broadcom, Meta, Tesla and Eli Lilly, all American. By sector, technology accounts for 29.84%, ahead of financials (16.15%), industrials (10.76%) and health care (10.19%). Buying the MSCI World therefore means buying the US stock market and its tech giants first, with a Japanese and European top-up.

The S&P 500: the 500 largest US companies

The S&P 500, created in 1957 and calculated by S&P Dow Jones Indices, follows 500 large US companies (503 shares on July 31, 2026, as some companies have two share classes). It covers about 80% of the value of the US stock market, according to the index overview. To join, a company must be American, be worth at least $22.7 billion and have made a profit over the latest quarter as well as over the last four quarters combined. A committee also keeps the sectors in balance.

It is more concentrated than the MSCI World: at the end of July 2026, its top ten holdings made up 37.6% of the total, and the largest, Nvidia, 7.6%. Since the US is nearly three quarters of the MSCI World, the two indices often move together; the difference lies in the 27% of the MSCI World invested outside the US, and in the mid-sized US companies it also holds.

What it has returned over a century

According to the historical data of Professor Aswath Damodaran (NYU Stern), the S&P 500 returned 10.02% a year on average from 1928 to 2025, with dividends reinvested, in dollars and before inflation. That average covers very different decades, with falls of more than 40% in 1929-1932, 2000-2002 and 2007-2009, and a 2000s decade that ended slightly down, dividends included.

MSCI ACWI and emerging markets: the real world index

The MSCI ACWI (All Country World Index) adds the large and mid-sized companies of 24 emerging countries to the MSCI World: 2,413 companies as of October 30, 2026, about 85% of the world's investable shares. The US still makes up 64.63%, ahead of Japan (5.08%) and Taiwan (3.23%), according to the ACWI factsheet. An ETF on the ACWI, or on another provider's “All World” index, is the simplest way to hold all the world's stock markets in a single line.

The MSCI Emerging Markets index holds only the 24 emerging countries: 1,165 companies, led by Taiwan (28.88%), China (20%), South Korea (19.66%) and India (11.73%). Comparing the two factsheets, emerging markets make up about 11% of the ACWI: holding an MSCI World ETF and an emerging markets ETF in a ratio close to 89% and 11% is roughly the same as holding the ACWI. These markets are bumpier: their worst fall reached 65% in 2007-2008, against 57% for the MSCI World.

Nasdaq-100, CAC 40, Stoxx 600: the other indices you come across

The Nasdaq-100 excludes banks and insurers, which makes it a technology and consumer index, more concentrated and more volatile than the S&P 500. The CAC 40 follows 40 large companies listed on Euronext Paris, many of which make most of their sales abroad. The Stoxx Europe 600 covers nearly 90% of the investable European stock market. With no US shares, these European indices are often used to rebalance a portfolio seen as too exposed to the United States.

MSCI World vs S&P 500: the differences

The S&P 500 is an investment in a single economy, the largest in the world and the one that has carried stock markets in recent years. The MSCI World adds the rest of the developed world, which slightly reduces single-country risk without removing it: with nearly three quarters in US shares, it remains closely tied to Wall Street. Neither is better in absolute terms. Over the ten years to the end of October 2026, US companies pulled the indices up; during the 2000s, the opposite happened. The choice depends on the diversification you want and on what you already hold elsewhere.

Past returns and worst falls

MSCI's factsheet publishes the returns of the three world indices, with gross dividends reinvested, in dollars, as of October 30, 2026:

Three lessons. First, the last ten years have been exceptional: 13.5% a year is well above the long-term average, and nothing says it will happen again. Second, the falls are deep: investors had to accept seeing their money cut by more than half in 2008-2009, and the MSCI World still lost 17.73% in 2022 alone. Third, these figures are in dollars: an investor whose currency is the euro, the pound or anything else also gains or loses the change in the dollar, which can add or remove several points a year.

The compound interest calculator lets you test what different returns produce over twenty or thirty years, with a cautious assumption as well as an optimistic one.

CW8 and the ETFs that replicate these indices

You cannot buy an index directly. You buy an index fund that reproduces it, usually an ETF, listed on the stock market like a share. CW8 is one of the best known in France: it is the ticker of the Amundi MSCI World Swap UCITS ETF EUR Acc, which replicates the MSCI World, reinvests dividends and held about €7.2 billion at the end of September 2026, according to its Amundi factsheet. “EPA:CW8”, the label shown on Google Finance, simply means it is listed on Euronext Paris.

Why an MSCI World ETF can go into a French PEA

France's PEA stock savings plan only accepts funds invested at least 75% in European shares. CW8 still qualifies thanks to synthetic replication: the fund holds a basket of European shares and signs a swap with a bank, which pays it the performance of the MSCI World. The same technique makes other ETFs eligible: in November 2026, Amundi PEA Monde (MSCI World), ticker DCAM, and iShares MSCI World Swap PEA, ticker WPEA, track the same index, as do ETFs on the S&P 500, the Nasdaq-100 or emerging markets. The guide to the PEA covers this account in detail, and the one on what an ETF is explains physical and synthetic replication, and where to hold ETFs in other countries.

What fees cost over twenty years

Two ETFs on the same index do not cost the same. According to the issuers' documents, ongoing charges are 0.38% a year for CW8 (factsheet of September 30, 2026), and 0.20% for DCAM (factsheet of July 31, 2026) as for WPEA. Take €10,000 invested at the start, then €200 a month for twenty years, €58,000 paid in, with an assumed return of 7% a year before fees:

The gap reaches €3,236 for the same index. Fees are not the only criterion: the actual performance gap with the index, the size of the fund, which makes buying and selling easier, and its track record count too. The price of a share, on the other hand, tells you nothing: a CW8 share was worth about €700 at the end of September 2026 and a DCAM share about €6 at the end of July, and neither is more expensive than the other. A pricey share only means investing in larger chunks.

Comparing two ETFs on an index

• The index tracked: MSCI World, ACWI or S&P 500, the difference in content matters more than anything else.
• Ongoing charges, taken each year from the fund's value.
• Tracking difference, the actual gap between the fund's performance and the index's, published in its documents.
• Fund size and trading volume, which affect the spread between buying and selling prices.
• Accumulating or distributing dividends, and PEA eligibility if that is the account you are using.
• The index currency: a euro-listed ETF on a mostly US index is still exposed to the dollar.

The limits of index investing

An ETF on a major index is a simple, low-cost way to diversify, but it has limits. Concentration first: when ten companies make up more than a quarter of the MSCI World and more than a third of the S&P 500, a fall in the tech giants is felt across the whole index. Market-cap weighting next: the index holds more of what has already risen, without asking whether it has become expensive. And currency risk, for an investor outside the dollar who mostly holds dollar shares.

Above all, a stock index never protects your capital. It suits money invested for at least five to ten years, after an emergency fund, as the guide on how to start investing in stocks explains. The one on where to put your money places these ETFs among other investments, according to the horizon of each sum.

Tradoshi's portfolio tracker accepts your ETFs, entered by hand or imported from your broker's statement, alongside your other accounts, with your cost basis.

This guide is educational and is not personalized investment advice. The ETFs mentioned are examples, not recommendations. Investing in shares carries a risk of capital loss, and past performance does not predict future performance. Figures as of November 2026.

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