Should a Global Portfolio Hedge Its Currency?

A US investor who buys a French stock owns two separate bets, whether they notice or not: the stock itself, priced in euros, and the euro against the dollar. If the stock rises 8% in euro terms but the euro falls 5% against the dollar over the same period, the investor's dollar return is not 8% — the currency move eats into it, landing near 2.6%. Currency hedging is the decision to strip that second bet back out using forward contracts, so the portfolio's return tracks the underlying asset, not the underlying asset and an FX position nobody explicitly chose to take.

The mechanics of a hedge

A currency forward locks in an exchange rate for a future date. To hedge a €10m equity position back to dollars, an investor sells €10m forward against dollars at today's forward rate, roughly matching the notional of the equity exposure. If the euro then falls against the dollar, the equity position's dollar value drops, but the forward contract gains an offsetting amount — the FX move cancels out of the total return. The catch: hedges need periodic rolling (typically monthly or quarterly, since forwards have fixed maturities) and the equity's own value moves daily, so the hedge ratio drifts and needs rebalancing, an ongoing operational cost.

Why hedge at all — and why not

The case for hedging: currency is roughly as volatile as many equity markets on its own, and unlike equity risk, it isn't obviously compensated — there's no long-run reason to expect a currency to trend up the way stocks trend up with earnings growth, so hedging removes a source of volatility without giving up much expected return. For bonds this argument is especially strong: a global bond portfolio's whole appeal is low volatility, and unhedged currency risk can be several times larger than the bond's own interest-rate risk, swamping the reason to hold bonds in the first place.

The case against hedging: hedging isn't free. The cost of a forward roughly equals the interest-rate differential between the two currencies (covered interest parity), so hedging a high-rate currency's exposure back into a low-rate currency is a negative carry cost, while hedging the other direction is a small gain. For equities, currency also sometimes cushions losses — a domestic recession that hits both stocks and the currency can be partly offset if the foreign currency happens to strengthen, and over long horizons currency moves have historically been closer to mean-reverting than persistent, muting their impact on multi-decade returns.

Worked example

A US investor holds $50m of European equities, unhedged. Over one year the MSCI Europe index returns 10% in local currency, but the euro depreciates 8% against the dollar. Unhedged dollar return: roughly $(1.10)(0.92) - 1 = 1.2\%$ — most of the local gain was erased by the currency move. Had the position been fully hedged, the investor would have captured close to the full 10% local return, minus the hedging cost. If euro short-term rates were 3.5% and dollar short-term rates were 5.25%, hedging euro exposure back to dollars earns the investor the 1.75-percentage-point rate differential as positive carry on top (selling the lower-yielding euro forward, buying the higher-yielding dollar) — so the hedged return in this scenario would be close to 10% plus roughly 1.75% of hedging carry, versus 1.2% unhedged. The currency move cost the unhedged investor around nine percentage points of return in this particular year; it could just as easily have added nine.

What this means in practice

Most institutional global portfolios hedge bonds close to fully, hedge developed-market equities partially (a common range is 30-50%, sometimes dynamically adjusted), and often leave emerging-market currency exposure unhedged because hedging instruments are expensive or illiquid there and because EM currency risk is sometimes viewed as a compensated risk premium rather than pure noise. The decision is really a bet on whether currency behaves more like an uncompensated volatility source (hedge it) or a diversifying, occasionally-compensated exposure (keep some of it).