For the better part of the past 15 years, international diversification has been a disappointment for US-based investors. The S&P 500 outperformed the MSCI EAFE index — which tracks developed market equities outside North America — by an average of approximately 6 percentage points per year between 2010 and 2023, one of the longest and most lopsided performance gaps between US and international equities in the post-war era. This persistent underperformance led many financial advisors and individual investors to reduce or eliminate international allocations, concluding that the diversification benefit was not worth the performance drag.
The 2024-2026 period has provided some vindication for those who maintained their international exposure, but the longer-term question of whether global diversification remains a sound strategy in a world of increasing geopolitical fragmentation and US corporate dominance deserves careful analysis rooted in the actual data.
The Valuation Case for International Exposure
The most compelling current argument for international diversification is valuation. The S&P 500 trades at approximately 21x forward earnings as of May 2026. The MSCI EAFE trades at approximately 13.5x forward earnings — a discount of approximately 36%. The MSCI Emerging Markets index trades at roughly 12x forward earnings.
Research Affiliates has published extensive analysis showing that starting valuation is among the most reliable predictors of subsequent 10-year equity returns. Their 2026 expected return forecasts project US large-cap equity returns of approximately 3.5% annually over the next decade, compared to approximately 7.2% for EAFE equities and 9.1% for emerging market equities. These projections embed mean-reversion assumptions that may or may not prove accurate — cheap things don’t automatically get more expensive — but the directional logic is sound: buying cheaper assets provides a larger margin of safety and a higher expected return.
The Currency Dimension
International equity returns for US investors are a combination of local market returns and currency returns. The strong dollar of 2022-2026 has been a meaningful headwind for US-based international investors: even when European, Japanese, and emerging market equities performed reasonably in local currency terms, the appreciation of the dollar against the euro, yen, and emerging market currencies reduced dollar-denominated returns.
Currency effects are inherently cyclical rather than structural, and the dollar appears to be approaching a point where further appreciation is constrained by purchasing power parity, US current account deficits, and the interest rate differential that has been the primary driver of recent dollar strength. If the Fed cuts rates more aggressively in the second half of 2026 and into 2027, narrowing the rate differential with European and Japanese rates, the dollar could weaken and provide a tailwind for international equity returns denominated in dollars.
For investors who want international exposure without currency risk, currency-hedged international ETFs eliminate the foreign exchange component of returns, providing pure local market exposure. Products like the iShares Currency Hedged MSCI EAFE ETF and similar offerings from Vanguard and WisdomTree allow US investors to hold international equities while paying to hedge out the currency risk through forward contracts.
Regional Differentiation: Where the Opportunities Are Clearest
The argument for international diversification is strongest in specific regions and sectors. Japan represents one of the more interesting developed market opportunities: the Tokyo Stock Exchange’s corporate governance reforms — which have pressured Japanese companies to improve return on equity, buy back shares, and increase dividends — have created a more shareholder-friendly environment that is beginning to translate into better equity returns. The MSCI Japan index was one of the best-performing developed market equity indices in 2023 and 2024, though performance has moderated in 2026 amid yen volatility and broader emerging growth concerns.
India has been discussed extensively as a growth market with genuine long-term demographic and structural tailwinds. European markets offer the defense sector opportunity described elsewhere, along with luxury goods and industrial companies at significantly lower valuations than US equivalents. UK equities — particularly the commodity-heavy FTSE 100 — offer above-average dividend yields and exposure to energy and mining sectors that provide useful portfolio diversification.
The Home Bias Problem
US investors have a particularly severe case of “home bias” — the tendency to overweight domestic equities relative to what portfolio theory would recommend. The US represents approximately 60-62% of world market capitalization, yet the median US investor holds approximately 85-90% of their equity portfolio in US equities, according to Vanguard’s annual research. This domestic concentration means that most US investors’ equity returns are almost entirely dependent on the performance of the US economy and corporate sector, despite the existence of a much larger international investment universe.
The academic research on home bias suggests that optimal diversification for US investors would involve international equity allocation of approximately 30-40% of the equity portfolio — a range that captures meaningful diversification benefits without excessive currency or geopolitical risk. In practice, many financial planners recommend 20-30% international allocation as a realistic target that most investors can maintain through performance droughts without abandoning.
Factors That Complicate the International Case
The case for international diversification is not without challenges. US corporate earnings quality is generally higher than international comparisons: US accounting standards are more stringent, corporate governance is stronger in most sectors, and the depth of US capital markets provides discipline that constrains earnings manipulation in ways that international markets sometimes do not.
US technology companies — which dominate global equity market capitalization and have driven the most significant value creation of the past two decades — are concentrated in the US market. An investor who holds only international equities misses the dominant global technology platforms: Apple, Microsoft, Alphabet, Amazon, Meta, and Nvidia are not accessible through European or Asian market indexes. The ETF Innovation provides some exposure to these companies through their global revenue footprints, but the equities themselves are listed in the US.
Geopolitical fragmentation adds a new layer of complexity to international investing that was less salient in the globalization era. Chinese equities carry explicit geopolitical risk that could result in forced selling by US investors if sanctions or market access restrictions are imposed. Russian equities became literally uninvestable overnight in 2022. These tail risks require more careful country-level assessment than broad “buy the index” approaches can provide.
Building an International Allocation
For most individual investors, low-cost, broadly diversified international index funds remain the most practical implementation of international exposure. The Vanguard Total International Stock ETF (VXUS), which covers approximately 8,000 companies across 45+ markets, provides comprehensive international exposure at a 0.07% expense ratio. For investors who want to be more selective, regional funds (EAFE-focused, emerging markets-focused) or country-specific ETFs allow more targeted expression of specific views.
The practical guidance that the data supports: maintain some meaningful international allocation — 20-30% of equity holdings is a reasonable target for most long-term investors — and rebalance periodically to maintain that allocation rather than allowing outperformance of US or international equities to progressively concentrate the portfolio. The diversification benefit of international exposure is not primarily about maximizing returns; it is about ensuring that portfolio outcomes are not entirely dependent on the continued exceptional performance of a single country’s equity market.
Sources: MSCI, Vanguard, Research Affiliates, Tokyo Stock Exchange corporate governance data, iShares ETF performance data, BIS, IMF
