What does top-10 concentration look like outside U.S. equities? The answer varies widely by region. As of April 2026, the top 10 companies by market cap accounted for 37.5% of the MSCI USA Index. That number was 32.4% for the MSCI Emerging Markets Index.

Developed international markets, however, tell a different story. The MSCI EAFE Index came in at 10.9%, less than one-third of U.S. levels. The MSCI ACWI Index, blending U.S. and international exposure, landed at 23.6%.

For equity index investors managing concentration risk, the question may be not which market to enter, but which index best reflects the diversification they’re seeking.