American investors exhibit extreme home bias, allocating over 80% of equity holdings domestically according to Vanguard research — despite the U.S. representing approximately 60% of global market capitalization. This concentration creates hidden risks that only become apparent during periods of U.S. underperformance.
Historical evidence shows U.S. dominance is cyclical, not permanent. Japanese stocks outperformed in the 1980s, European and emerging markets led in the 2000s, and international stocks have beaten U.S. stocks in roughly 40% of rolling 10-year periods since 1970 per Dimson-Marsh-Staunton data.
Vanguard research suggests an optimal international allocation of 20-40% of equity holdings improves the efficient frontier — reducing portfolio volatility without sacrificing expected returns. The 3-fund portfolio approach (U.S. total market, international total market, total bond) provides global diversification at minimal cost through index funds like VXUS (0.07% expense ratio).
Originally published on WealthWise OS.