U.S. stocks dominated portfolios for over a decade. The performance gap between American and international markets created home bias that seemed justified by results.
2025 reversed the trend. International markets delivered performance that reminded investors why global diversification matters.
The 2025 Performance Reversal
In 2025, the Morningstar Global Markets ex-US Index returned 32%, versus 18% for the Morningstar US Market Index. The strength in non-USD assets continued into 2026, with foreign stock performance still benefiting from a weaker dollar.
Investing 101 traditionally teaches portfolio diversification, but many investors stopped applying this globally after years of U.S. outperformance. The correlation between developed markets ex-US and U.S. stocks over the 3-year period ending 2022 was 0.92, meaning they moved almost identically and provided minimal diversification benefit.
By the end of 2025, that correlation declined to 0.71. The difference matters:
- Correlation of 0.92: international stocks provide little diversification
- Correlation of 0.71: international stocks move somewhat independently
- Lower correlation means better portfolio risk reduction
The declining correlation restored the diversification benefit that justified global allocation.
Why Correlation Matters
Portfolio risk depends on how assets move together. When all holdings rise and fall in sync, diversification provides no protection.
The 0.92 correlation through 2022 meant U.S. and international stocks crashed together during downturns and rallied together during recoveries. Holding both didn’t reduce volatility.
The 0.71 correlation by end of 2025 means they still move in the same general direction but with meaningful differences. International stocks can rise when U.S. stocks fall modestly, and vice versa.
This independence reduces total portfolio volatility without sacrificing returns.
The Currency Dimension
International investing adds currency exposure that doesn’t exist in domestic-only portfolios. When the dollar weakens, foreign currency gains add to international stock returns. When the dollar strengthens, currency losses subtract.
The 2025 international outperformance partly reflected dollar weakness. Foreign stocks rose in local currency terms, then the weaker dollar amplified returns for U.S. investors.
Currency can enhance or diminish returns:
- Weak dollar scenario: Foreign stocks up 10% in local currency, dollar down 5% = 15.5% total return
- Strong dollar scenario: Foreign stocks up 10% in local currency, dollar up 5% = 4.8% total return
The same local return produces different results based on currency moves.
Managing Currency Exposure
Investors can choose how much currency risk to accept:
- Unhedged approach: Accept full currency exposure, gaining from dollar weakness but losing from dollar strength
- Hedged approach: Use currency hedging to remove currency impact, capturing only local stock returns
- Partial hedge: Hedge 50% of currency exposure, balancing both effects
Each approach has tradeoffs. Unhedged adds volatility but captures currency diversification. Hedged reduces volatility but costs money through hedging fees.
The 2025 performance shows unhedged worked well. But the 2015-2020 period favored hedged approaches as the dollar strengthened.
The 120-Year Case
Global investment research for 2026 emphasizes that long-run data over 120 years supports international diversification across equities, bonds, and currencies.
The 120-year timeframe captures multiple currency regimes, war periods, economic cycles, and market structures. Across all these conditions, diversification improved risk-adjusted returns.
Short-term performance favors different markets during different periods. U.S. stocks led 2010-2020. Japanese stocks led the 1980s. European stocks had strong periods in the 1990s and 2000s.
No investor knows which market will lead next decade. Diversification ensures participation regardless of which region outperforms.
The Rebalancing Benefit
Global diversification creates systematic rebalancing opportunities. When U.S. stocks outperform for years, they become larger portfolio percentage. Rebalancing sells some U.S. exposure and buys more international.
This forces selling strength and buying weakness. When international markets then outperform, the portfolio captures more of the gain because rebalancing increased the allocation.
The 2025 reversal rewarded investors who maintained international exposure despite underperformance. Those who eliminated international stocks after years of U.S. dominance missed the 32% return.
The Implementation Options
Investors can access international markets through several vehicles:
- International stock funds: Diversified exposure to developed markets outside U.S.
- Emerging market funds: Higher growth potential with higher volatility
- Regional funds: Specific exposure to Europe, Asia-Pacific, or other regions
- Country-specific funds: Concentrated bets on individual countries
- Global funds: Worldwide exposure including U.S. stocks
Each vehicle offers different risk-return profiles and currency exposures.
The Developed vs Emerging Split
Developed international markets include Japan, UK, Germany, France, Canada, Australia, and similar economies. These offer moderate growth with established market infrastructure.
Emerging markets include China, India, Brazil, Taiwan, Korea, and developing economies. These offer higher growth potential with more volatility and political risk.
A balanced approach allocates to both. Common splits include 70% developed, 30% emerging or 80% developed, 20% emerging.
The allocation depends on risk tolerance and growth objectives.
The Sector Exposure Difference
International markets provide different sector exposures than U.S. markets. Europe has more financials and industrials. Asia has more technology manufacturing. Emerging markets have more commodities and materials.
This sector diversity provides additional diversification benefit. When U.S. technology dominates American indices, international exposure reduces tech concentration.
The 2025 performance partly reflected sector differences. U.S. markets concentrated in mega-cap tech faced valuation pressure. International markets with broader sector balance avoided this concentration risk.
