Should You Invest Internationally?
Updated ·5 min read·Reviewed by the StockTools.ai Research Team
- ▸Home-country bias is the well-documented tendency to overweight your own country’s stock market relative to its share of global market value.
- ▸US investors in particular tend to hold far more US-only exposure than the US’s share of world market cap would suggest — though the US being unusually large makes some tilt defensible.
- ▸International stocks are not perfectly correlated with US stocks, so adding them can lower portfolio-level volatility even when their expected returns look similar.
- ▸The counterarguments are real: unhedged currency risk, large US companies already earning revenue worldwide, and long stretches where US stocks have simply outperformed.
- ▸There is no single correct international allocation — reasonable, well-informed portfolios span a wide range.
What home bias is, and why almost everyone has it
Home-country bias is the tendency of investors, in nearly every country studied, to hold a much bigger slice of their own market than that market’s actual weight in global investable assets would call for. It is not a US-only quirk — Japanese investors overweight Japanese stocks, UK investors overweight UK stocks, and so on. The US case gets the most attention because the US stock market has recently made up a very large share of global market capitalization, so a fully "US-heavy" portfolio is less of a distortion than it would be for, say, a Canadian or Australian investor doing the same thing with their own smaller market. Even so, many US investors hold close to 100% domestic equities, noticeably more than a global-market-cap weighting would put in the US.
The reasons are more psychological and practical than analytical. Familiarity plays a large role — people trust the companies, brands, and news coverage they encounter every day, and US financial media covers US markets far more than it covers Frankfurt or Tokyo. There are also legitimate frictions: domestic funds are sometimes cheaper, tax treatment of foreign dividends and funds can be less favorable, and skipping currency conversion removes a layer of complexity. None of that makes the bias irrational exactly — it makes it understandable — but understandable and optimal are not the same thing.
The diversification case for going global
The core argument for international exposure is not that foreign stocks will necessarily outperform — nobody can promise that — it is that international and US stocks do not move in perfect lockstep. Different economies run on different cycles, different central banks, different currencies, and different sector mixes, so their returns diverge at least some of the time even when both broadly go up over long periods. That imperfect correlation is the entire mechanical reason diversification can reduce risk without necessarily reducing expected return: combining two assets that do not move identically smooths out the ride even if each one, held alone, would have looked similarly volatile.
This is the same logic used to justify holding more than one stock in the first place, just applied one level up, at the country level. A portfolio that is 100% one country’s stock market is making a concentrated bet on that country’s companies, regulators, currency, and economic cycle all at once. Spreading equity exposure across multiple countries and regions is a way of not needing any single economy to be the one that performs well in a given decade.
The honest counterarguments
The case against loading up on international stocks is not just home bias talking — it has real substance. Unhedged foreign holdings carry currency risk: even if a foreign company’s stock price is flat in its local currency, your return in dollars moves with the exchange rate, adding a layer of volatility that has nothing to do with the business itself. Many of the largest US companies already sell a substantial share of their products and services abroad, so a "US-only" portfolio is not actually pure domestic exposure — it comes with meaningful indirect international revenue baked in, which somewhat blunts the argument that US-only investors have zero global exposure.
History also has to be dealt with honestly: there have been long multi-year, even decade-plus, stretches where US stocks meaningfully outperformed international stocks, and other stretches where the reverse was true. Anyone who tilted heavily toward international during a strong US run has felt the opportunity cost, just as anyone who avoided international during a weak US run has felt the opposite. International funds can also carry higher expense ratios and less favorable tax treatment of foreign dividends than comparable domestic funds, which is a real, ongoing cost rather than a one-time consideration.
A range, not a single right answer
Given all of that, there is no universally correct international allocation — reasonable, informed people land in different places. Some hold international weightings close to global market-cap proportions on the theory that markets already price in each country’s expected risk and return. Others deliberately keep a home tilt, reasoning that they spend, save, and eventually retire in their home currency, so some extra weight in their own market reduces certain practical risks even as it concentrates others. Both are defensible starting points; what is harder to defend is landing at either extreme — all-domestic or all-international — without having actually weighed the tradeoffs.
The more useful question is usually not "what is the correct number" but "have I chosen my international weighting on purpose, or by default." If a portfolio is 100% domestic simply because that is what felt familiar when the account was opened, it is worth at least checking how that compares to a global benchmark and deciding, deliberately, whether the resulting currency exposure, cost tradeoffs, and diversification benefit line up with your own reasoning — rather than treating the current mix as neutral just because it is the default.
FAQ
What is home-country bias?
The well-documented tendency of investors to hold much more of their own country’s stock market than that market’s share of global market capitalization would suggest. It shows up in nearly every country studied, not just the US, though it gets the most attention in the US because the US market is unusually large.
Is it wrong for US investors to hold mostly US stocks?
Not necessarily — the US being a very large share of global market value makes some domestic tilt more defensible than it would be for investors in smaller markets. But many US portfolios sit at or near 100% domestic, which is more concentrated than a global-market-cap weighting alone would explain.
Why would adding international stocks reduce risk if their returns are similar to US stocks?
Because risk reduction from diversification comes from imperfect correlation, not from picking the higher-returning asset. If international and US stocks do not move in perfect lockstep, combining them can smooth portfolio-level volatility even when each, held alone, looks similarly volatile. See how correlation drives this in the diversification guide.
Do US companies already give me international exposure?
Partially. Many large US companies earn significant revenue abroad, so a US-only portfolio is not purely domestic in an economic sense. That said, the stock still trades on the US market and is exposed to US regulatory, currency, and market-cycle factors, so it is not a full substitute for holding actual international equities.
What is the right percentage to hold internationally?
There is no single correct figure — reasonable portfolios range from something close to global market-cap weights to a meaningful home tilt. The more important step is deciding your allocation deliberately, weighing currency risk, cost, and diversification benefit, rather than defaulting to whatever your portfolio happened to start with.
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Educational only — not financial advice. Concepts simplified for clarity; markets are messier than definitions.