International vs US Investing Calculator: How Much Diversification Do You Need?

From 2010 to 2024, US stocks crushed international stocks. The S&P 500 returned about 14% annually. Developed international markets returned around 6%. Emerging markets about 4%.

That 14-year stretch has convinced many US investors that international diversification is a mistake. History suggests otherwise.

The Decade-by-Decade Comparison

| Decade | US Stocks (Annualized) | International Developed | |--------|----------------------|------------------------| | 1970s | 5.9% | 10.4% | | 1980s | 17.5% | 22.8% | | 1990s | 18.2% | 7.3% | | 2000s | -0.9% | 2.2% | | 2010s | 13.6% | 5.8% | | 2020-2024 | 16.1% | 8.9% |

International outperformed in the 1970s, 1980s, and 2000s. The US dominated in the 1990s, 2010s, and 2020s. The long-run averages are much closer than recent performance suggests.

The decade you happen to invest in can determine your outcome. No one knows which geography outperforms over the next 20 years.

Why International Diversification Still Makes Sense

Valuation differences. US stocks trade at historically elevated valuations (P/E ratios). International and emerging market stocks trade at lower valuations. Lower starting valuations historically correlate with higher future returns.

Currency diversification. A falling US dollar increases the return on international investments when measured in dollars. US-only portfolios are fully exposed to dollar strength/weakness.

Global market share. Non-US companies represent 40% of global market capitalization. Excluding them entirely is a large bet against 40% of the world's publicly traded companies.

Correlation benefit. International stocks do not move in perfect lockstep with US stocks. Adding an uncorrelated asset reduces portfolio volatility even if it does not increase returns.

How Much to Allocate Internationally

| Approach | US % | International % | |----------|------|----------------| | US-only | 100% | 0% | | Light international | 80% | 20% | | Market weight | 60% | 40% | | Vanguard recommendation | 60% | 40% | | Global market cap weight | 60% | 40% |

Most financial advisors recommend 20-40% international within the equity allocation. The exact amount is less important than having meaningful exposure.

The Costs and Frictions of International Investing

Higher expense ratios. Vanguard Total International Stock ETF (VXUS): 0.07% expense ratio vs 0.03% for VTI (US total market). A small but real drag.

Foreign tax withholding. Many countries withhold taxes on dividends paid to US investors (typically 15-25%). In a taxable account, you can claim a foreign tax credit to offset this. In an IRA, the withholding is lost — there is no credit mechanism.

Currency risk. International returns in USD include currency movement. A 10% gain in a Japanese stock is partially offset if the yen falls 5% against the dollar during the same period.

Tracking error. International markets have more variance in returns, meaning some years are notably better or worse than US markets for reasons unrelated to fundamentals.

Developed vs. Emerging Markets Split

Within international allocation, you can split between developed markets (Europe, Japan, Australia) and emerging markets (China, India, Brazil, Taiwan).

| Category | Example Countries | Historical Volatility | |----------|-----------------|----------------------| | US | United States | Baseline | | Developed International | Germany, Japan, UK | ~15% higher than US | | Emerging Markets | China, India, Brazil | ~35% higher than US |

A simple split: 70% US, 20% developed international, 10% emerging markets. This provides global exposure while limiting the higher volatility of pure emerging market allocation.

See Best Investing Platforms for low-cost international index fund options.

Use the CalcMoney Investment Return Calculator to model different international allocation scenarios over your investment horizon.

Frequently Asked Questions

Do US companies already provide international exposure?

Somewhat. Large US multinationals earn 30-40% of revenue internationally. However, owning US-listed multinationals does not provide the same diversification benefit as owning foreign companies, because the stock still trades in USD and follows US market sentiment. The correlation with the S&P 500 is much higher than with foreign equity indexes.

Should I hedge currency risk in international funds?

Currency hedging adds cost and is most valuable for short time horizons. For long-term investors (10+ years), currency fluctuations tend to average out. Most long-term international index funds are unhedged. Currency-hedged versions are available but carry an additional 0.3-0.5% annual cost.

Is now a good time to increase international allocation?

International stocks are at historically low valuations relative to US stocks based on CAPE ratios. Historically, low valuations correlate with better future returns. However, the same was true in 2010, and US stocks significantly outperformed for the next 14 years. Timing international allocation based on relative valuations is risky. A consistent long-term allocation is more reliable than tactical shifts.