S&P 500, Nasdaq-100 or MSCI World: what each one is and what the data say

The S&P 500 holds about 500 large US companies (503 share lines, because some have two share classes). A committee at S&P Dow Jones Indices picks them, and each one weighs according to its market cap.

The Nasdaq-100 is the 100 largest non-financial companies listed on the Nasdaq market, American or not: it has no banks or insurers, and it does have companies such as ASML, Arm, MercadoLibre or Ferrovial. It is also cap-weighted, with caps on how much each company can weigh.

The MSCI World is 1,280 large and mid-sized companies from 23 developed countries, about 85% of each country's stock market value. It excludes emerging markets such as China, India or Brazil: those are in the MSCI ACWI.

Sources: S&P Dow Jones Indices methodology, the Nasdaq-100 fact sheet (Nasdaq, 6/30/2026) and the MSCI World fact sheet (MSCI, 8/31/2026).

The MSCI World spreads money more, but less than its name suggests: with 72.1% in the United States, its largest holdings are the same as the S&P 500's. NVIDIA weighed 5.6% in the MSCI World, 7.6% in the Nasdaq-100 and 7.7% in the S&P 500.

Between the S&P 500 and the Nasdaq-100 the overlap is even larger. With Nasdaq's official list of September 17, 2026 and this site's company pages from the next day:

• 85 of the Nasdaq-100's 100 companies are in the S&P 500, and they make up 91% of the Nasdaq-100 by market cap.
• Those 85 are 54.9% of the S&P 500 by market cap. Nine of its ten largest companies are in the Nasdaq-100; the missing one is Berkshire Hathaway, a financial company.
• The 15 that are not are foreign companies listed on Nasdaq (ASML, Arm, PDD, MercadoLibre, Shopify, Ferrovial…) or US companies the S&P 500 committee has not added.

By sector, each provider uses its own classification and they cannot simply be subtracted. In MSCI's, technology was 29.8% of the MSCI World; in Nasdaq's, which puts Alphabet and Meta in technology, 68.5% of the Nasdaq-100. How the S&P 500 splits by sector, company by company, is in the S&P 500 sectors.

The 5- and 10-year returns are annualized. Volatility comes from monthly returns, the way MSCI computes it. Both worst drawdowns were the financial crisis, bottoming on March 9, 2009: SPY's from its October 9, 2007 peak and the MSCI World's from October 31.

Over ten years, the S&P 500 beat the MSCI World by 1.7 points a year. Year by year:

SPY came out ahead in 10 of these 14 years; the MSCI World in 2012, 2017, 2022 and 2025. Since large US companies are the bulk of both, the differences come mostly from the 28% of the MSCI World outside the United States (Japan, the UK, Canada, France…) and from the dollar against those currencies.

The worst drawdown for both was 2022: the Nasdaq-100's from December 2021 to December 2022, SPY's from December 2021 to September 2022. Measured with month-end closes; with daily closes it is somewhat larger. The Nasdaq-100's volatility and drawdown were calculated by this site from the 120 months in the official fact sheet.

The Nasdaq-100 came out ahead in 7 of the 9 years and lost in 2021, narrowly, and in 2022, by a lot. With dividends, SPY returned 15.40% a year over those ten years; the Nasdaq-100 pays less in dividends, so its real lead was somewhat smaller than the table shows.

Ten very good years for technology are not the whole story. According to a Nasdaq Indexes study from January 2021, from 1995 to 2020 the Nasdaq-100 returned 13.98% a year with dividends and the S&P 500 10.01%, but with volatility of 25.82% against 16.57%. That period includes the dot-com bust: the index nearly quintupled between 1998 and 2000 and fell by the same proportion over the next two years (the study).

Each figure links to its official fact sheet, with data as of August 31, 2026. For the ETFs it is the TER (total expense ratio); for the funds, ongoing charges. This manager has no index fund on the Nasdaq-100 in this range. On top come the broker's charges: custody, trading or currency exchange.

The differences look small, but they compound: 0.23 points more a year, over 20 years, take about 4.5% of the final value (0.9977 to the 20th power is 0.955). US-listed funds such as SPY or QQQ serve here as yardsticks; a retail investor in the EU usually cannot buy them, because they do not publish the key information document that EU rules require.

• Mutual fund (not listed). If you redeem units and the money goes straight into another fund, no tax is due at that moment: the new units keep the purchase value and date of the old ones. This is the traspaso in article 94 of the Spanish income tax law. It must go through entities registered with the CNMV, a foreign fund must be registered with the CNMV to be sold in Spain, and the money cannot pass through your account.
• ETF (listed fund). The same article excludes it from the traspaso. Since January 1, 2022 (Law 11/2021) the exclusion also covers ETFs listed on foreign exchanges, according to the Spanish Tax Agency's manual. Selling one ETF to buy another means declaring the gain or loss.
• On a final sale, the same. The gain on a fund or an ETF goes to the savings tax base, taxed at 19% to 30% in 2026. Dividends paid by a distributing class are taxed each year; an accumulating class does not pay them out.

This is the general case for a resident of Spain; yours may have particulars. How US shares bought directly are taxed, with dividends and the W-8BEN, is in the guide to how US stocks are taxed in Spain.

Which has returned more: the S&P 500, the Nasdaq-100 or the MSCI World?

Over the last ten years, the Nasdaq-100. From June 30, 2016 to June 30, 2026 it rose 21.22% a year on price alone, against 13.55% for SPY. As of August 31, 2026, with dividends and in dollars, SPY returned 15.28% a year over ten years and the MSCI World 13.56%. With other dates the order changes: the Nasdaq-100 fell much harder in 2000-2002 and in 2022. These are past returns.

What is the difference between the S&P 500 and the MSCI World?

The S&P 500 is about 500 large US companies. The MSCI World is 1,280 large and mid-sized companies from 23 developed countries, but the United States weighed 72.1% on August 31, 2026. It does not include emerging markets such as China, India or Brazil.

Does holding both the S&P 500 and the Nasdaq-100 diversify?

Not much. On September 17, 2026, 85 of the Nasdaq-100's 100 companies were also in the S&P 500, and they made up 91% of the Nasdaq-100 by market cap. The nine companies in the MSCI World's top ten lines are in all three indices.

How are index funds and ETFs taxed differently in Spain?

With a non-listed mutual fund, a resident of Spain can move the money to another fund without paying tax at that moment (a traspaso), under article 94 of the Spanish income tax law. With an ETF they cannot: since 2022 that exclusion also covers ETFs listed on foreign exchanges, and every sale is taxed. When finally sold, both are taxed the same way, as savings income.

How much does an index fund or ETF on these indices cost?

As a reference, iShares' fact sheets as of August 31, 2026 gave expense ratios of 0.07% a year for its S&P 500 ETF, 0.20% for its MSCI World ETF and 0.30% for its Nasdaq-100 ETF. Other products have different costs, and the broker may charge on top.

• Different periods and measures. The Nasdaq-100 fact sheet ends on June 30 and is price only; the MSCI World's ends on August 31 and includes gross dividends. SPY is a real fund and already deducts its fee (0.09% a year); indices have no costs.
• In dollars. An investor in euros also gains or loses on the exchange rate. How much that changed the numbers over the last 25 years is in $100 a month in the S&P 500.
• Ten years are not a full cycle. The decade to 2026 was exceptional for large tech companies; in 2000-2002 the opposite happened.

More guides: equal-weight vs. cap-weighted S&P 500, three ways to invest in the S&P 500 and how to read the Sharpe ratio and max drawdown; all of them in the guides. The terms, in the glossary. What each company in the index pays out, in S&P 500 dividends, and what an amount in SPY would have become from the date you choose, in the S&P 500 calculator.