Index scope explained

S&P 500, MSCI World or FTSE All-World – what is actually inside?

The important first difference is not which line recently rose more. It is which countries and company sizes the rulebook is designed to represent. An index is the recipe; a fund is one product that may track it.

S&P 500

Large U.S. companies

Market scope: United States
Company sizes: Large companies
United States share: All of it, by definition
Emerging markets: No

A focused U.S. equity building block. It is not a world index, even when its companies earn revenue globally.

MSCI World

Developed markets

Market scope: Developed countries
Company sizes: Large and mid-sized companies
United States share: About 72 percent
Emerging markets: No

“World” here means developed markets. Emerging markets and small companies need a separate allocation if you want them.

FTSE All-World

Developed plus emerging markets

Market scope: Developed and emerging countries
Company sizes: Large and mid-sized companies
United States share: About 62 percent
Emerging markets: Yes

One market-cap-weighted global index. “All-World” still does not mean every listed company: small and micro companies sit outside this version.

Country weights follow market prices and move with them. The shares above are approximate and were reviewed on 3 September 2026; the point is the gap between two indexes both called “world”, not the second decimal. Providers can classify the same market differently: South Korea is a prominent example, classified as emerging by MSCI and developed by FTSE Russell at this review date.

The names answer different geographic questions

S&P 500 asks how large U.S. companies perform. MSCI World joins large and mid-sized companies across developed markets. FTSE All-World adds emerging markets to a developed-market core. Comparing their past lines before choosing the intended scope reverses the decision order.

Global revenue is not global market allocation

A U.S.-listed company can sell worldwide, but its shares still sit in a U.S. market allocation. Revenue exposure, listing country, currency experience and index country classification answer different questions.

Market-cap weighting follows market prices

Larger free-float market values receive larger weights. That keeps the index investable and self-adjusting, but it can also create substantial country, sector or company concentration. “Many holdings” and “evenly diversified” are not synonyms.

An index is not the ETF you buy

Several funds can track the same index with different ongoing costs, replication, tracking difference, domicile, tax treatment, distribution policy and trading currency. Choose the market scope first, then compare products that implement it.