Bogle on Global Investing: Why He Says Your Backyard Has Diamonds

Book: Common Sense on Mutual Funds: Fully Updated 10th Anniversary Edition by John C. Bogle ISBN: 978-0-470-59748-4

This is the chapter where Bogle goes against the crowd. And honestly? It’s one of the most interesting chapters in the whole book precisely because a lot of smart people disagree with him.

He opens with a story about Al Hafed, a wealthy Persian farmer. Al Hafed sold his farm and traveled the world searching for diamonds. He spent everything, found nothing, and died poor. Meanwhile, back on his original farm, someone discovered one of the largest diamond mines in history.

The moral is obvious. Sometimes what you’re looking for is right where you started.

Bogle’s Controversial Take

Most financial advisors will tell you to put 30-40% of your stock portfolio in international funds. It’s standard advice. The reasoning is solid on paper: different economies grow at different rates, and spreading your money around the world reduces your risk if any one country stumbles.

Bogle disagrees. Not completely, but substantially. He argues that international investing is NOT essential for a well-diversified portfolio. And he has several reasons.

First, the United States has the most productive economy in the world. It has the deepest, most liquid capital markets. It has the strongest legal protections for investors. If you’re going to concentrate your investments anywhere, this is the place to do it.

Second, currency risk. When you invest in international stocks, you’re not just betting on those companies. You’re also betting on the exchange rate between the dollar and whatever currency those stocks trade in. If the foreign market goes up 10% but that country’s currency drops 10% against the dollar, you’ve made nothing. Currency adds a whole layer of volatility that has nothing to do with how good the underlying companies are.

Third, the academic theory of global diversification hasn’t actually delivered in practice. The idea of a “global efficient frontier” suggests that mixing international stocks with domestic stocks should improve your risk-adjusted returns. But Bogle argues the real-world data doesn’t support this as strongly as the theory predicts.

US Companies Are Already Global

Here’s the point that makes this argument really stick. The biggest US companies are already global companies. Apple sells phones in 175 countries. Coca-Cola operates in over 200 countries. Many large US companies earn 30-50% of their revenue from overseas.

So when you buy a total US market index fund, you’re already getting global economic exposure through the companies you own. You’re just not taking on the currency risk and the additional costs of investing through foreign markets.

This is something that doesn’t get talked about enough. People think “I only own US stocks, so I’m not globally diversified.” But if those US companies are making billions in Europe, Asia, and Latin America, you absolutely have global exposure. Just indirectly.

International Fund Managers Are Even Worse

Remember how most US fund managers can’t beat their benchmarks? International fund managers have even worse track records. The costs are higher (foreign markets have higher transaction costs, custody fees, and tax complexities), the information is harder to get, and the results are worse.

So if active management is a bad deal domestically, it’s an even worse deal internationally. The fees eat even more of your returns, and the managers are even less likely to make up for those fees with superior stock picking.

If you do invest internationally, Bogle says, at least use index funds. Of course.

But Here’s the Problem

This is where I have to be honest about Bogle’s advice. This was his most controversial view, and a lot of very smart, very credible people disagree.

The US market makes up roughly 60% of global stock market capitalization. That means 40% of the world’s investable stock market is outside the US. Ignoring that is a big bet on one country, no matter how good that country’s economy is.

There have been entire decades where international stocks crushed US stocks. The 2000s were a prime example. If you were 100% US from 2000 to 2009, you got almost nothing. International stocks did significantly better.

And the “US companies have global revenue” argument has limits. A US company earning money in Europe still has its stock priced based on US market conditions, US investor sentiment, and US valuations. Owning actual European companies gives you exposure to European valuations, which can be very different.

So while Bogle’s argument is thought-provoking, many investors and advisors believe some international allocation is smart. The debate is really about how much, not whether.

What Bogle Actually Recommends

Bogle isn’t saying zero international. He’s saying don’t overdo it. If you want international exposure, he suggests capping it at 20% of your equity portfolio. That gives you some diversification benefit without taking on too much currency risk or paying too much in fees.

And of course, whatever international allocation you choose, use index funds. An international total market index fund or a developed markets index fund will give you broad exposure at low cost.

How to Think About This Today

If you’re building a portfolio in 2026, here’s a reasonable way to think about this chapter. Bogle makes a strong case that you don’t NEED a ton of international exposure. The US market has been incredible. And US companies do give you indirect global exposure.

But having some international allocation (15-30% is a common range) gives you insurance against the possibility that the US won’t always dominate. No country stays on top forever. Just ask British investors from the early 1900s, when the UK was the world’s financial center.

The real takeaway from this chapter isn’t “avoid international stocks.” It’s “don’t blindly follow the conventional wisdom that you need 40% international.” Think about what you actually need, keep costs low, and don’t pay active managers to pick foreign stocks for you.

The diamonds might be in your backyard. But it doesn’t hurt to check the neighbors’ yard too. Just don’t pay someone a fortune to help you dig.

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