How much diversification benefit do international equities actually provide?

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AcadiFi · Accepted Answer

International diversification still matters but the benefit is smaller than it was 30 years ago. **Empirical baseline**: Rolling 10-year correlation of MSCI World ex-US against S&P 500 was around 0.45 in the 1980s, rose to 0.75–0.85 in the 2010s, and sits around 0.78 today. Cross-market correlation spikes during stress (0.90+ in March 2020), exactly when you want diversification most. **Sources of remaining benefit**: (1) Different sector composition — Europe is heavier in financials and industrials, US is heavier in tech. (2) Different monetary policy cycles — Japan and Europe lagged US hiking cycle. (3) Currency exposure provides an additional diversifier or risk, depending on hedging. (4) Country-specific factors — Australian commodity exposure, Swiss pharma, Korean tech hardware. Worked example: An investor named Camila at Brookridge Wealth holds a $1M all-US equity portfolio with ~17% annualized volatility. Replacing 30% with MSCI EAFE (vol 16%, correlation 0.78 with S&P) reduces portfolio vol to ~15.8%, a 1.2 percentage point reduction — modest but meaningful over long horizons. **Tail risk remains correlated**: In Q1 2020, S&P 500 was down 20% and EAFE was down 23%. Diversification doesn't protect against global shocks but DOES protect against country-specific policy, currency crises, and regulatory events. ```mermaid graph LR A[US Equity Only
Vol: 17%] --> B[Add 30% EAFE] B --> C[Vol: 15.8%] B --> D[Lower
concentration risk] B --> E[Currency
diversification] ``` Bottom line: the diversification benefit has shrunk but has not disappeared. Combined with higher home-country valuation risk in a concentrated US market, the case remains compelling.

How much diversification benefit do international equities actually provide?

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