I remember talking to a client about ten years ago. He was adamant. "Why would I bother with Europe or Japan? My 401k is all in the S&P 500, and it's crushing everything." Back then, it was hard to argue. The US market was on a tear, fueled by tech giants and cheap money. Fast forward to today, and that conversation feels different. The narrative hasn't changed much—headlines still tout US dominance—but the numbers and the underlying dynamics are telling a more complex story. If you're trying to decide how much of your portfolio should be in US stocks versus international ones, you're not just betting on companies. You're betting on currencies, central bank policies, and which region will invent the next world-changing sector.

What You'll Learn

Why US Stocks Won the Last Decade (It Wasn't Just Tech)

Let's get the obvious out of the way. From 2010 through much of the 2020s, US stocks, as measured by the S&P 500, dramatically outperformed broad international indexes like the MSCI EAFE (Europe, Australasia, Far East). We're talking about a gap that turned a 60/40 US/International portfolio into a serious drag on returns. But attributing this win solely to "American innovation" is a surface-level take that can lead to bad future decisions. The outperformance rested on three interconnected pillars.

The Dollar Was a Silent Turbocharger

This is the part most DIY investors miss. When the US dollar gets stronger, it directly reduces the returns of foreign stocks for a US-based investor. Think of it this way: you buy shares of a German company priced in euros. The company does well, and the stock rises 10% in euro terms. But if the euro falls 5% against the dollar during that same period, your net return in US dollars is only about 5%. For over a decade, we had a potent mix of relative US economic strength, higher interest rate expectations, and global crises that sent money fleeing to the perceived safety of the dollar. This currency headwind was a constant weight on international returns reported in USD. A report from the Federal Reserve has extensively documented dollar strength in this period.

Sector Concentration: Winner Takes All

The US market became hyper-concentrated in the one sector that defined the era: technology. By the early 2020s, just a handful of mega-cap tech stocks made up over 25% of the S&P 500. Meanwhile, international indexes like the MSCI EAFE remained heavily weighted in financials, industrials, and consumer staples—sectors that grew, but not at the explosive, multiple-expanding rate of tech. So, you weren't just investing in "the US economy." You were making an outsized bet on the success of a specific business model (software, digital ads, cloud computing) that happened to be headquartered in Silicon Valley. This wasn't a bet on American factories; it was a bet on global digital monopolies.

A crucial nuance: Many of these US tech giants get more than half their revenue from outside the United States. So, in a way, a US-heavy investor was still getting international exposure—but only through the lens of a few American-headquartered companies. This is very different from owning a Japanese robotics firm, a German luxury carmaker, or a Korean semiconductor foundry.

Valuations Expanded, Not Just Earnings

Performance comes from two places: earnings growth and people's willingness to pay more for those earnings (valuation expansion). The US had a massive dose of both. Investor enthusiasm, fueled by low rates and a "there-is-no-alternative" mindset, kept pushing price-to-earnings ratios higher. International markets saw earnings growth too, but their valuations remained stubbornly lower, often languishing. This created a perception gap: US stocks were "proven winners" deserving a higher price, while international stocks were "risky laggards." This is a classic momentum cycle, and it can't run forever.

The Case for Looking Abroad Now

Past performance is the most dangerous phrase in investing. The factors that drove US dominance are not immutable laws. In fact, several of them look stretched or are actively reversing. Here’s why ignoring international stocks today might be the modern equivalent of my client's home bias a decade ago.

Valuation Disparity Has Reached Extreme Levels. This is the simplest, most mathematical argument. As of recent data, the S&P 500's cyclically-adjusted P/E ratio (CAPE) has often been nearly double that of the MSCI EAFE index. History doesn't guarantee mean reversion, but it strongly suggests it. You're paying a huge premium for US earnings growth, which may or may not materialize. International markets are simply cheaper, offering more earnings per dollar invested.

The Dollar Cycle Might Be Turning. The US dollar's long bull run is facing headwinds. Differences in interest rate policies between the US Federal Reserve and other central banks are narrowing. If the dollar weakens, it acts as a tailwind for international returns for US investors. That silent drag becomes a silent boost.

Sector Leadership Rotates. The next decade's winning sector might not be software-as-a-service. It could be green energy infrastructure, automation, biotechnology, or advanced manufacturing—areas where European, Japanese, or Korean firms have deep expertise. An internationally diversified portfolio gives you a ticket to those innovations without relying on a single country's stock market to produce all the winners.

Look at this comparison of key characteristics. It's not about which is "better," but about understanding the trade-offs you're making.

Characteristic US Stocks (S&P 500 Focus) International Stocks (Developed Markets ex-US)
Recent Historical Returns (USD, ~10 yrs) Higher Lower
Current Valuation (Avg. P/E) Significantly Higher Significantly Lower
Sector Exposure Concentrated in Tech, Communication Services More balanced across Financials, Industrials, Consumer
Currency Effect for USD Investor Neutral (investing in home currency) Can be major headwind or tailwind
Dividend Yield Generally Lower Generally Higher
Primary Risk Perception Valuation / Concentration Risk Political / Economic / Currency Risk

How to Build Your Global Portfolio (A Practical Framework)

So, what should you actually do? Throwing darts at a world map isn't a strategy. Here’s a framework I use with investors, moving from the simple to the more nuanced.

The Core Foundation: Global Market Weight

The purest, most neutral starting point is to mirror the global market. As of now, US stocks make up about 60% of the world's total stock market capitalization. The rest is international. A 60% US / 40% International split is a rational, unemotional baseline. You're not betting on a winner; you're owning a slice of global business productivity. This is what a low-cost total world stock index fund (like VT) does automatically.

Most people's portfolios are wildly overweight the US compared to this. That's not necessarily wrong, but it is an active bet that needs justification.

Tactical Tilts: When to Deviate

This is where your view comes in. If you believe the valuation gap is unsustainable, you might tilt to 50% US / 50% International, or even 40/60. This is a conscious bet on mean reversion. Conversely, if you have deep conviction in US technological and regulatory advantages, you might hold 70% or 80% US. The key is to know why you're deviating and what would make you change your mind.

A specific tool: Consider allocating a portion of your international holding to a currency-hedged ETF. This removes the currency rollercoaster and lets you bet purely on foreign company performance. It's a cleaner play if you think foreign stocks will rise but are unsure about the dollar.

Implementation: Keep It Simple and Cheap

Complexity is the enemy of execution. You don't need ten different funds.

  • One-Fund Solution: Vanguard Total World Stock ETF (VT). It's all in one, global weight, done.
  • Two-Fund Solution: Vanguard Total Stock Market ETF (VTI) for US + Vanguard Total International Stock ETF (VXUS) for non-US. This gives you control over the ratio and is still incredibly cheap.
  • For a tilt: Add iShares Currency Hedged MSCI EAFE ETF (HEFA) to the two-fund mix if you want hedged exposure.

Rebalance once a year, or when your allocation drifts by more than 5% from your target. That's it. The goal is to set a plan that fits your belief about US vs international stocks over time and stick to it through the inevitable cycles where one part zigs while the other zags.

Your Questions Answered

I keep hearing international stocks have "underperformed for decades." Is there any point where they do better?
The "decades" frame is misleading and depends entirely on your start and end date. Look at the period from 2002 to 2007, or the entire 1970s. International stocks handily beat US stocks. Performance runs in long, secular cycles. The 2010-2020 US bull run is one cycle. The cycle before that favored international. Believing the most recent cycle will repeat indefinitely is a common behavioral mistake called recency bias.
Doesn't investing in big US companies like Apple give me enough global exposure since they sell everywhere?
It gives you global revenue exposure, which is not the same as global market diversification. You're still exposed solely to US corporate governance, US accounting standards, US tax policy, and US investor sentiment. When US tech falls out of favor, all those stocks tend to move together, regardless of where their customers are. True diversification means owning companies that operate under different economic cycles, regulatory environments, and investor cultures. A German chemical company reacts to different stimuli than a US social media company.
International stocks seem riskier because of political instability and currency issues. Why take that risk?
You're identifying real risks. But the US has its own set of concentrated risks (political polarization, debt levels, market concentration) that are often discounted because they're familiar. Currency swings are a double-edged sword—they can hurt returns, but they can also boost them. More importantly, adding assets that are risky on their own can make your overall portfolio less risky if they don't move in lockstep. The low correlation between US and international markets over time is the whole point of diversification. It's about smoothing the ride, not just chasing the highest return.
What's a common mistake people make when they finally decide to add international stocks?
They do it at the wrong time and in the wrong way. The worst move is to go from 0% to 30% international after the US has had a bad year and international has had a good year. You've just bought high (international) and sold low (US relative to its peak). You're chasing performance backwards. The second mistake is picking a complex, high-cost "emerging markets growth" fund because it sounds exciting, instead of using a broad, low-cost index fund for the bulk of the allocation. Start with a small, sustainable allocation to a total international index fund as part of a plan, and increase it gradually with new contributions.