Dominant U.S. Stock Market?

As of November 2025, the MSCI All Country World Index (ACWI) allocates about 65% to U.S. stocks. Is this allocation to a single country crazy high? In the November 2025 revision of their brief paper entitled “How Much Is Too Much? Part 1: Why 60% in US Equities Isn’t as Crazy as It Might Sound”, Arnaud Battistella and Nicholas McLoughlin assess this allocation by deriving the expected returns implied by ACWI allocations across regions (U.S., Europe ex UK, UK, Japan, Pacific ex Japan and Emerging Markets). Using mid-2025 ACWI allocations and monthly returns for specified regions in U.S. dollars during December 1987 through May 2025, they find that:

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