The Dollar and Your Portfolio: Why the U.S. Currency Drives Your Returns
The dollar and your portfolio: why the U.S. currency affects every investment you own
The dollar, as the world’s reserve and invoicing currency, exerts a mechanical influence on the performance of any international portfolio — through exchange rates, capital flows, and commodity prices — in ways that non-U.S. investors systematically underestimate.
A European investor in a World ETF is, whether they realize it or not, exposed to the dollar for more than 60% of their allocation. Understanding that exposure starts with understanding how the U.S. currency works.
An MSCI World ETF shows +15% over the year in dollars. The European investor holding the same ETF sees +8% in their brokerage account. The difference — seven percentage points of performance — does not come from hidden fees or a calculation error. It comes from the euro’s move against the dollar. When the dollar strengthens, the euro-denominated performance of a dollar-denominated asset is higher than its dollar performance. When the dollar weakens, the opposite happens: part of the gain in dollars is absorbed by the euro’s appreciation.
This seemingly simple mechanism has profound implications. The dollar is not just any currency. It is the currency in which most international transactions, foreign-exchange reserves, emerging-market debts, and commodities are denominated. Understanding how the dollar functions in the global system means understanding a variable that mechanically affects the performance of almost every asset class — whether or not you invest in the United States.
The dollar as a reserve currency: a structural role, not a cyclical one
According to IMF data, the dollar accounts for about 58% of global foreign-exchange reserves. That share has declined since the 2000s (it was 72% in 2001), but it remains unmatched: the euro, the second reserve currency, does not exceed 20%.
This reserve-currency status is not symbolic. It has mechanical consequences. When central banks around the world accumulate reserves in dollars, they buy dollar-denominated assets — mainly U.S. Treasury bonds. This structural demand supports both the dollar’s value and the price of U.S. government bonds. It also creates dependence: if a confidence shock caused a meaningful share of holders to move away from the dollar, the impact on U.S. interest rates and on the global financial system would be substantial.
For a European investor, this reality means the dollar is not just an exchange-rate risk: it is a systemic risk. The dataset tracking the dollar and global crises since 1973 shows that every major financial crisis over the past fifty years had a dollar component — either because its sudden surge squeezed non-U.S. borrowers with dollar debt, or because its weakness reflected a rush into other assets.
Real rates and capital flows: the mechanism behind dollar moves
The dollar does not move randomly. Over the medium term, its path is driven by real interest-rate differentials between the United States and the rest of the world.
The mechanism works as follows: when U.S. real rates are higher than those in the euro area or Japan, international capital flows toward dollar assets to capture that yield advantage. This influx of capital pushes the dollar higher. When the differential narrows — because the Fed cuts rates or because the ECB raises them — the flow reverses and the dollar weakens. This capital-flow channel is the dominant driver of exchange-rate movements over 6- to 24-month horizons.
The historical series of U.S. real rates helps place this dynamic in long-term context. Periods of high real rates in the United States (the early 1980s, 2022–2024) have consistently coincided with periods of dollar strength. Periods of low or negative real rates (2010–2021) have corresponded to a more subdued, or even weak, dollar.
This correlation between real rates and the dollar is not perfect — it is distorted by crises, central-bank intervention, and geopolitical shocks. But it provides a robust framework for reading the dollar’s directional trend. And that direction has direct consequences for
Mis à jour : 30 March 2026
This article provides economic and financial analysis for informational purposes only. It does not constitute investment advice or a personalized recommendation. Any investment decision remains the sole responsibility of the reader.