U.S. vs International Allocation: How Much Should You Diversify Abroad?

American investors typically hold 70-80% of their equity allocation in U.S. stocks—despite the U.S. representing only 42% of global equity market capitalization (MSCI, 2024). This "home bias" has been rewarded handsomely for the past 15 years: U.S. stocks returned 12.8% annualized (2009-2024) while international developed markets returned 5.7% and emerging markets returned 4.2%. But historical U.S. outperformance creates recency bias risk. The decade before (1999-2009), international stocks outperformed the U.S. by 4% annually.

The practical question isn't whether U.S. dominance continues. It's what allocation balances the risk of continued U.S. outperformance against the risk of U.S. reversion to the mean—and how to structure international exposure to maximize diversification benefit while managing currency risk.

Home Bias (The Behavioral Default)

Home bias isn't irrational—it has legitimate explanations—but it does create concentration risk.

Why investors overweight domestic:

• Familiarity: You know Coca-Cola; you don't know Nestle's business model
• Currency simplicity: No exchange rate exposure to manage
• Information access: U.S. financial reporting is transparent, timely
• Tax efficiency: Foreign dividend withholding creates drag
• Performance anchoring: Recent U.S. returns make alternatives look unappealing

Current home bias levels (U.S. investors):

• Average 401(k) allocation to international: 22%
• Vanguard target-date funds: 40% international (their recommendation)
• Market-cap weight (theoretically "correct"): 58% international

The cost of extreme home bias:

If you held 100% U.S. stocks from 2000-2010, you experienced:

• S&P 500 return: -0.9% annualized (lost decade)
• MSCI EAFE return: +1.2% annualized
• MSCI Emerging Markets: +9.8% annualized

A 60/40 U.S./International portfolio returned +4.1% annualized—turning a lost decade into modest gains.

The point is: Home bias costs compound in periods of U.S. underperformance. You don't know when those periods will occur. Diversification is insurance against regimes you can't predict.

Developed Markets (EAFE) vs Emerging Markets

International exposure isn't monolithic. Developed markets (Europe, Australia, Japan) have different risk/return profiles than emerging markets (China, India, Brazil).

EAFE characteristics (developed ex-U.S.):

Countries: Japan (22%), UK (14%), France (11%), Switzerland (10%), Germany (8%), others

Sector weights vs S&P 500:

• Financials: 18% (vs. 13% U.S.)—more bank-heavy
• Industrials: 16% (vs. 9% U.S.)—manufacturing exposure
• Healthcare: 13% (vs. 12% U.S.)—similar
• Technology: 9% (vs. 32% U.S.)—major underweight
• Consumer Staples: 10% (vs. 6% U.S.)—defensive tilt

Key insight: EAFE is essentially "value and cyclical" exposure versus U.S. "growth and tech" exposure. When value outperforms growth, EAFE tends to outperform. When tech dominates, EAFE lags.

Emerging Markets characteristics:

Countries: China (24%), India (20%), Taiwan (18%), South Korea (12%), Brazil (5%), others

Structural differences:

• Higher GDP growth (5-6% vs. 2% developed)
• More volatility (standard deviation 22% vs. 15% developed)
• Currency risk (often larger swings than developed)
• Political/governance risk (regulatory uncertainty)
• Sector concentration: Taiwan/Korea = semiconductors, China = tech/consumer

Performance comparison (2014-2024):

The durable lesson: Emerging markets haven't rewarded risk over the past decade. But this underperformance occurred after EM outperformed massively (2000-2010). Mean reversion in international allocations is measured in decades, not years.

Currency Hedging (When It Matters)

When you buy international stocks in an unhedged fund, you get equity return plus currency return. If the euro rises 5% against the dollar while European stocks return 8%, your dollar return is roughly 13%. If the euro falls 5%, your return is only 3%.

The hedging decision framework:

Arguments for hedging:

• Eliminates currency volatility from equity returns
• Currency movements are largely unpredictable
• Reduces portfolio standard deviation by 2-3%
• Makes international allocation feel "cleaner"

Arguments against hedging:

• Currency diversification is valuable in its own right
• Dollar weakness often coincides with international stock outperformance
• Hedging costs money (0.1-0.5% annually)
• Natural hedge: Dollar weakness means your foreign assets buy more when converted

Historical data (EAFE hedged vs unhedged):

The practical framework:

• For developed markets: Moderate hedge (50%) or unhedged is reasonable
• For emerging markets: Unhedged is standard (hedging EM currencies is expensive and less liquid)
• For tactical investors: Hedge when you expect dollar strength; unhedge when you expect dollar weakness

Currency hedging cost reality:

• EUR/USD hedge: ~0.1-0.2% annually
• JPY/USD hedge: ~0.3-0.5% annually (rate differential driven)
• EM currencies: 1-3% annually (often prohibitive)

The point is: For most investors, unhedged international exposure is fine. The diversification benefit of currency exposure roughly offsets the volatility cost over long horizons.

Correlation Benefits (The Real Reason to Diversify)

Diversification works when assets don't move together. International stocks provide imperfect correlation with U.S. stocks—the relationship isn't zero, but it's low enough to reduce portfolio volatility.

Correlation data (1990-2024, monthly returns):

What correlations mean for portfolios:

A 0.75 correlation means that when U.S. stocks fall 10%, international stocks typically fall 7.5%—not the full 10%. This partial cushioning, repeated over time, reduces portfolio volatility.

Volatility reduction math:

Assume both U.S. and international have 15% standard deviation, and correlation is 0.75.

100% U.S. portfolio: 15% volatility 70% U.S. / 30% International: 13.9% volatility (7% reduction) 50% U.S. / 50% International: 13.4% volatility (11% reduction)

The diversification benefit is modest but real—and it compounds over time into meaningfully different outcomes.

Crisis correlation caveat: During severe market stress (2008, 2020), correlations spike toward 1.0. Diversification provides less protection exactly when you want it most. This is why international allocation reduces average volatility but doesn't eliminate tail risk.

Allocation Framework (Practical Recommendations)

The spectrum of reasonable allocations:

Factors that justify higher U.S. allocation:

• You earn foreign income (already internationally diversified)
• Strong conviction in continued U.S. tech dominance
• Short time horizon (less time for mean reversion)
• Tax sensitivity (foreign dividend withholding matters)

Factors that justify higher international allocation:

• Long time horizon (decades for mean reversion)
• Value-oriented strategy (international is cheaper)
• Concern about U.S. dollar strength reverting
• Want to match global market cap weights

Within international, the split:

Most advisors recommend roughly 70% developed / 30% emerging within international allocation. This weights by market cap while acknowledging EM's higher volatility.

Example allocation (moderate investor, $100,000 equity):

• U.S. stocks: $65,000 (65%)
• International developed: $24,500 (24.5%)
• Emerging markets: $10,500 (10.5%)

Valuation Context (Are Cheap Markets Actually Cheaper?)

International stocks trade at significant discounts to U.S. stocks on most metrics.

Current valuations (December 2024):

The valuation gap is historically wide:

• Average P/E discount (EAFE vs S&P 500, 2000-2024): 15%
• Current P/E discount: 36%

Why international might deserve a discount:

• Lower growth (Europe demographics, Japan stagnation)
• Less tech exposure (structural sector difference)
• Governance/shareholder return differences
• Currency headwinds (strong dollar)

Why the discount might be excessive:

• Europe has significant quality companies (LVMH, ASML, Novo Nordisk)
• Japan is undergoing corporate governance reform
• EM growth eventually translates to equity returns
• Mean reversion in relative valuations historically occurs

The durable lesson: Cheap doesn't mean imminent outperformance. International stocks have been "cheap" for a decade. But wide valuation gaps eventually close—you just can't predict when.

Mitigation Checklist (Structuring International Exposure)

Essential (high ROI)

These decisions matter most:

• Minimum 20% international to capture meaningful diversification
• Maximum 50% international unless specifically matching global market cap
• Split 70/30 developed/EM within international (market cap weight)
• Use low-cost index funds (expense ratio matters more over long periods)

High-impact (implementation choices)

For investors refining their approach:

• Consider currency-hedged developed markets if concerned about dollar weakness
• Review tax location: hold international in taxable accounts for foreign tax credit
• Rebalance annually to maintain target allocation

Optional (for active investors)

If making tactical allocation decisions:

• Monitor relative valuations (CAPE ratio spreads)
• Track dollar direction for currency impact
• Watch for EM-specific catalysts (China policy, commodity cycles)

Next Step (Put This Into Practice)

Calculate your actual international allocation across all accounts.

How to do it:

1. List all investment accounts (401(k), IRA, taxable)
2. For each fund, look up geographic allocation on Morningstar
3. Multiply fund value by international percentage
4. Sum international exposure across all accounts
5. Divide by total equity value

Example:

• 401(k): $200,000 in target-date fund (40% international) = $80,000 international
• IRA: $50,000 in S&P 500 fund (0% international) = $0 international
• Taxable: $50,000 in Total International (100% international) = $50,000 international
• Total international: $130,000 / $300,000 = 43%

Interpretation:

• Below 20%: Significant home bias—consider adding international
• 20-40%: Moderate diversification—reasonable for most investors
• 40-60%: Strong diversification—matches or exceeds typical recommendations
• Above 60%: Overweight international—intentional underweight to U.S.

Action: If your international allocation is below 20%, calculate what rebalancing would look like. A single international index fund (VXUS, IXUS) provides complete developed + emerging exposure at minimal cost.