How does currency movement affect equity returns?

Imagine you buy a Japanese stock. The business does great—it doubles in yen terms. But while you owned it, the yen weakened 40% against the dollar. Your $100 investment doubled to 200 in yen, but when you convert back to dollars, you get only $120. The stock's brilliant performance was cut in half by currency movement.

This is the hidden tax on international investing that many beginners ignore until it's too late. Currency can add or subtract 10-20% annually to returns on foreign stocks. Over long periods, currency movements average out somewhat due to interest rate parity and mean reversion. But over shorter periods—months to years—currency can dominate returns. A top-down investor doesn't just pick stocks; he or she also takes a view on currency.

Quick definition: Currency exposure is the sensitivity of your investment returns to changes in foreign exchange rates. When you buy foreign stocks, you're simultaneously taking a position on the foreign currency relative to your home currency.

Key takeaways

• Currency volatility can dwarf stock returns, with annual moves of 10-20% common, making FX a primary return driver for international portfolios
• Unhedged equity returns equal stock returns plus currency returns, so ignoring currency is ignoring half the risk-return profile
• Interest rate differentials drive currency over long periods, with higher-yielding currencies tending to depreciate over time (interest rate parity)
• Currencies mean-revert but on a 5-10 year timeline, making long-term hedging expensive without a clear benefit
• Home currency appreciation creates a headwind for international stocks, while depreciation creates tailwinds you don't control
• Hedging costs money, eroding long-term returns unless you have conviction that a currency is overvalued
• Emerging market currencies tend to depreciate over decades against developed-market currencies, a secular headwind many investors don't anticipate

Currency as an explicit bet

When you buy a stock in a foreign country, you're making two simultaneous decisions, though only one may be conscious. You're deciding:

1. The stock is attractive (based on fundamentals, valuation, growth)
2. The foreign currency is reasonably valued or will appreciate (even if unstated)

If you hate the second proposition—if you believe the foreign currency is overvalued—you're fighting an additional headwind. A 10% stock gain combined with a 15% currency depreciation produces a 6% net loss to a domestic investor.

This is why currency views matter in top-down analysis. Before allocating capital to an emerging market country, a top-down investor asks: What's the currency outlook? Is the currency fairly valued? Are interest rates attractive enough to compensate for expected depreciation?

A currency is "fairly valued" by interest rate parity when interest rate differentials are captured in forward exchange rates. If US rates are 5% and Brazilian rates are 11%, the forward market should price in a decline in the Brazilian real to compensate. The currency will weaken enough that the interest rate advantage is offset by FX depreciation. This prevents arbitrage.

But in the short and medium term, currencies deviate from parity due to sentiment, growth differentials, and capital flows. These deviations are opportunities or risks for equity investors.

The interest rate parity framework

Interest rate parity (IRP) is the foundation of currency economics. It states that a currency's expected depreciation should offset interest rate differentials. If US rates are 4% and Japanese rates are 0.5%, the yen should appreciate about 3.5% per year (on average) to equalize returns.

This works mathematically like this:

Expected yen appreciation = US interest rate - Japanese interest rate

If this didn't hold, arbitrageurs would borrow cheap yen, buy US bonds, and lock in risk-free profit. Competition would push the yen stronger until IRP was restored.

IRP is not a prediction of what will happen—it's an equilibrium relationship. But it's important for equity investors because it tells us what currency movement is "expected" given interest rates. If IRP predicts yen appreciation and the yen instead depreciates, that's a surprise that adds to (or subtracts from) equity returns.

A practical example: If US rates are 5% and British rates are 4%, IRP predicts sterling should appreciate about 1% annually against the dollar. If you buy UK stocks and sterling does appreciate 1% as expected, the currency effect roughly offsets the interest rate differential. If sterling appreciates 5%, you get a bonus. If it depreciates, you get a penalty.

Unhedged equity returns: Stock plus currency

The total return to a US investor buying foreign stocks is:

Unhedged return = (1 + stock return) × (1 + currency return) - 1

If a German stock returns 15% in euros and the euro strengthens 5% against the dollar, the unhedged return to a US investor is:

(1.15) × (1.05) - 1 = 20.75%

Conversely, if the euro weakens 5%, the return falls to:

(1.15) × (0.95) - 1 = 9.25%

Same stock, same business performance, but a 11.5 percentage-point difference in returns due to currency movement. This illustrates why currency risk is not trivial—it can double or halve returns depending on FX moves.

Over long periods, currency volatility tends to average out (mean reversion). A currency that strengthens one decade often weakens the next. But an investor with a 5-year time horizon or less cannot rely on mean reversion. Currency risk is real and often dominates stock-specific risk.

This is why many international equity funds show unhedged and hedged return series separately. The difference between the two is pure currency contribution.

The currency drag of emerging markets

One of the most persistent findings in emerging market research is currency depreciation. Emerging market currencies tend to depreciate against developed-market currencies over long periods—not always, but as a secular trend.

Why? Several reasons:

1. Inflation differential: Emerging markets often have higher inflation than developed markets. Higher inflation leads to currency depreciation (Purchasing Power Parity).
2. Capital flight risk: When crisis hits, money leaves emerging markets for developed-market safety. Capital outflows weaken the currency.
3. Lower interest rates in EM: As emerging economies develop and stabilize, real interest rates fall. Lower rates = currency depreciation over time.
4. Terms of trade: Many emerging markets export commodities and import manufactured goods. Commodity price weakness depresses currencies.

Because of this secular headwind, emerging market equity returns (in developed-market currencies) have been significantly lower than would be implied by emerging market stock performance alone. A 12% annual equity return in an emerging market becomes 8-9% to a developed-market investor if the currency is depreciating 2-3% annually.

This doesn't mean emerging markets are bad investments. It means you must account for currency drag when evaluating expected returns. Some investors solve this by hedging their emerging market currency exposure. Others accept it as the cost of emerging market participation.

Hedging currency exposure

One solution to currency risk is hedging: using financial instruments (currency forwards, options) to lock in an exchange rate. If you own British stocks and want to eliminate currency risk, you can sell pounds forward, locking in a known dollar proceeds.

Hedging eliminates currency volatility but costs money. The cost is the difference between the spot rate and the forward rate, which reflects the interest rate differential. If US rates are 2% higher than UK rates, the forward pound rate is 2% lower than today's spot rate. Your hedged return is capped at the lower forward rate.

The formula is:

Hedged return ≈ (1 + stock return) × (1 + foreign interest rate - home interest rate)

If UK stocks return 12% and UK rates are 2% while US rates are 5%, the hedged return to a US investor is approximately:

12% + (2% - 5%) = 9%

The 3% interest rate differential is the "cost" of hedging. You're paying away that differential to eliminate currency risk.

When does hedging make sense? When you believe:

1. The currency is overvalued and will weaken beyond what interest rate parity predicts. Hedging locks in that value now.
2. You want to isolate stock selection from currency. If your view is purely on the stock, not the currency, hedging removes the currency noise.
3. Your time horizon is short (under 5 years) and you cannot tolerate currency volatility. Hedging provides certainty.

When does hedging not make sense? When you:

1. Believe the currency is undervalued and will strengthen. Unhedged, you capture that appreciation as a bonus.
2. Accept currency volatility as part of the return profile. Over decades, currencies mean-revert.
3. Are willing to accept the interest rate differential cost for the diversification benefit. This is often the case with long-term emerging market investors.

Emerging markets and currency volatility

Emerging market currencies are far more volatile than developed-market currencies. The Indian rupee, Brazilian real, Mexican peso, and Thai baht can move 15-20% in a year. Developed-market currencies like the euro, pound, and yen typically move 5-10% annually.

This volatility is not random. It's driven by:

• Capital flows: When global risk appetite is high, capital flows into emerging markets, strengthening the currency. When risk appetite falls, money flees, weakening it.
• Commodity prices: Many emerging markets depend on commodity exports. When commodity prices fall, the currency weakens.
• Political and economic shocks: Elections, policy changes, crises cause currency swings.
• Contagion: Problems in one emerging market spread to others. A Chinese slowdown weakens all EM currencies.

Because of this volatility, emerging market equity returns have a huge currency component. A 20% stock return combined with a 25% currency depreciation produces a 2.5% net return. A 10% stock return combined with a 10% appreciation produces 21%. Currency can make or break emerging market returns.

This is why some long-term emerging market investors hedge currency exposure. They want emerging market equity exposure without currency volatility. They pay the interest rate differential to remove that volatility.

Real currency moves and dollar strength

The dollar is the world's reserve currency and tends to strengthen during crises when investors flee to safety. When the Fed tightens rates and US growth is strong, the dollar tends to strengthen. When the Fed eases and growth slows, the dollar tends to weaken.

Consider these periods:

2014-2016: Strong dollar period. The Fed began tightening (ending QE3), US growth was accelerating, oil was collapsing. The dollar index rose 25%. Unhedged international stock returns lagged US stocks massively because of FX headwinds.

2017-2019: Weak dollar period. Fed paused hikes, global growth was recovering, capital flowed into emerging markets. The dollar weakened 10%. International stocks outperformed partly because of currency tailwinds.

2021-2022: Strong dollar again. The Fed hiked aggressively to combat inflation, rate differentials widened sharply. The dollar index rose 20%. International stocks underperformed despite stable business performance.

2023: Dollar reversal. As rate hikes paused and recession fears rose, the dollar weakened. International stocks benefited from currency tailwinds.

These multi-year currency trends can add or subtract 5-10% annually to international returns. Over a decade, such trends can boost returns by 50%+ or reduce them similarly.

Real-world examples

Japanese stocks 2009-2019: Japanese equities returned over 10% annually in yen for this period due to Abenomics and earnings growth. But the yen strengthened 25% against the dollar. US investors earned only 2-3% annually because currency gains went to Japanese buyers, not foreign investors. Currency was the story.

Emerging markets 2001-2007: Commodity boom and capital inflows strengthened EM currencies. MSCI Emerging Markets returned 30%+ annually, but much was currency appreciation. When the 2008 crisis hit and currencies reversed, EM stocks fell even harder than developed markets.

European stocks 2015: The ECB expanded its quantitative easing program, weakening the euro 15% against the dollar. European stocks fell modestly in euros but were up 5-10% to US investors due to currency tailwinds.

Indian rupee 2022-2023: The rupee weakened roughly 10% against the dollar as the Fed hiked rates faster than the RBI. Indian stocks returned double digits in rupees, but US investors gained less due to currency headwinds.

Mexican peso 2020-2024: Mexico benefited from US nearshoring and strong growth. The peso strengthened 30% against the dollar. Mexican stocks soared in peso terms but US investors got an additional currency bonus.

Common mistakes with currency

Mistake 1: Assuming currency "washes out" over time. Many investors believe currency volatility is noise that averages to zero over decades. This ignores secular trends like emerging market currency depreciation and interest rate differentials. Currency doesn't wash out; it compounds.

Mistake 2: Ignoring currency when comparing international stocks. A "10% return" in Germany might be 15% in euros and a 5% euro appreciation, or 8% in euros and a 2% depreciation. Always check whether returns are in local currency or your home currency before comparing.

Mistake 3: Hedging blindly without a view. Paying the interest rate differential to hedge "just in case" is expensive over time. Hedge only if you have a specific view that the currency is overvalued.

Mistake 4: Misunderstanding carry trade profits. Some investors buy high-yielding currencies to capture interest rate differentials. But if interest rate parity holds, the currency depreciates, offsetting the yield. This works only if you're right that the currency is undervalued.

Mistake 5: Overlooking currency in emerging market allocation. When considering emerging markets, many investors focus entirely on valuations and growth, ignoring currency risk. Emerging market valuations can look cheap until currency depreciation is factored in.

Mistake 6: Thinking home currency is always safe. Your home currency can weaken too. A US investor oversimplifies by assuming the dollar will always be strong. In some eras (2003-2007, 2020-2023), the dollar weakened and international stocks outperformed.

FAQ

Q: Should I hedge my international stock exposure?

A: Only if you have a specific view that the currency is overvalued. If you're neutral on currency and want pure exposure to international stocks, consider whether the hedging cost (the interest rate differential) is worth it. For long-term diversified portfolios, many investors accept currency volatility rather than pay hedging costs.

Q: How much of my international return is currency versus stocks?

A: Vary by period. Over 2008-2014, currency was actually negative for most international investors due to dollar strength—stocks would have looked even worse without currency appreciation in some regions. In 2017-2019, currency contributed 5-7% annually to international returns as the dollar weakened. Check your returns in local currency versus your home currency to decompose this.

Q: Is there a "best" currency hedge ratio?

A: Some investors hedge 50% of international exposure, unhedging the other 50%. This is a compromise that captures some currency upside but reduces some volatility. Others use 0% (fully unhedged) or 100% (fully hedged). Your choice should depend on your belief about the currency and your risk tolerance.

Q: What happens to emerging market currencies during crises?

A: They weaken sharply as capital flees to developed markets and reserve currencies. This creates a double hit: emerging market stocks fall and currencies depreciate. This is why emerging markets are riskier for investors in developed markets. You get not just equity drawdown but currency drawdown too.

Q: Can I profit from currency movements alone?

A: Yes, through currency trading or carry trades. But for an equity investor, currency is a secondary bet. Focus on stock selection first. Currency movements are important for understanding total returns, but they're highly unpredictable for the short to medium term.

Q: Should I adjust my valuation metrics for currency?

A: Partially. When comparing a German company to a US company, use the same reporting currency for both (typically dollars). Account for the fact that the German company's earnings may be helped or hurt by euro strength/weakness. Some analysts use normalized exchange rates rather than current rates to smooth out temporary FX moves.

Q: How do global companies hedge their own currency exposure?

A: Most multinational companies have natural hedges—they earn revenue in multiple currencies and spend in multiple currencies. If Microsoft earns 40% of revenue in euros but spends only 10% in euros, it's net long euros and benefits from euro strength. This is why multinational equity returns are partially hedged naturally.

Related concepts

• Interest rate parity — The relationship between interest rates and currency movements that eliminates arbitrage
• Purchasing power parity — The theory that currencies adjust to equalize purchasing power across countries
• Capital flows — Money moving into or out of a country, which affects currency demand and supply
• Currency forwards — Financial instruments used to lock in exchange rates and hedge currency risk
• Carry trade — Borrowing in low-yielding currencies and investing in high-yielding currencies to capture the interest differential

Summary

Currency exposure is not a side effect of international investing—it's a primary return driver that deserves conscious analysis. Every dollar you invest abroad is simultaneously a bet on the foreign stock and the foreign currency. Ignoring the currency component is ignoring half the risk-return equation.

The key insights are:

1. Currency movements are large, often 10-20% annually, and can dwarf stock-specific returns.
2. Hedging has a cost, the interest rate differential, so hedge only if you believe the currency is overvalued.
3. Currencies mean-revert over decades, but over years, trends persist.
4. Emerging markets face currency headwinds, with currencies tending to depreciate over time.
5. Dollar strength and weakness cycles create periods of international stock outperformance and underperformance.

By explicitly considering currency in your allocation decisions, you elevate your top-down analysis. You'll avoid the surprise that a 15% stock gain became a 5% net loss because you weren't paying attention to FX. And you'll capture opportunities when currency is mispriced relative to interest rate differentials or fundamentals.

Next

Proceed to The interest-rate environment and stocks, where we explore how central bank policy, rates, and the yield curve shape stock valuations and returns.

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Five articles on global allocation and currency factors (2,187 words completed).