Covered interest arbitrage

Covered interest arbitrage is an arbitrage trading strategy whereby an investor capitalizes on the interest rate differential between two countries by using a forward contract to cover (eliminate exposure to) exchange rate risk. Using forward contracts enables arbitrageurs such as individual investors or banks to make use of the forward premium (or discount) to earn a riskless profit from discrepancies between two countries' interest rates. The opportunity to earn riskless profits arises from the reality that the interest rate parity condition does not constantly hold. When spot and forward exchange rate markets are not in a state of equilibrium, investors will no longer be indifferent among the available interest rates in two countries and will invest in whichever currency offers a higher rate of return. Economists have discovered various factors which affect the occurrence of deviations from covered interest rate parity and the fleeting nature of covered interest arbitrage opportunities, such as differing characteristics of assets, varying frequencies of time series data, and the transaction costs associated with arbitrage trading strategies.

An arbitrageur executes a covered interest arbitrage strategy by exchanging domestic currency for foreign currency at the current spot exchange rate, then investing the foreign currency at the foreign interest rate. Simultaneously, the arbitrageur negotiates a forward contract to sell the amount of the future value of the foreign investment at a delivery date consistent with the foreign investment's maturity date, to receive domestic currency in exchange for the foreign-currency funds.

For example, as per the chart at right consider that an investor with $5,000,000 USD is considering whether to invest abroad using a covered interest arbitrage strategy or to invest domestically. The dollar deposit interest rate is 3.4% in the United States, while the euro deposit rate is 4.6% in the euro area. The current spot exchange rate is 1.2730 $/€ and the six-month forward exchange rate is 1.3000 $/€. For simplicity, the example ignores compounding interest. Investing $5,000,000 USD domestically at 3.4% for six months ignoring compounding, will result in a future value of $5,085,000 USD. However, exchanging $5,000,000 dollars for euros today, investing those euros at 4.6% for six months ignoring compounding, and exchanging the future value of euros for dollars at the forward exchange rate (on the delivery date negotiated in the forward contract), will result in $5,223,488 USD, implying that investing abroad using covered interest arbitrage is the superior alternative.

...
Wikipedia