Interest rate parity is a no-arbitrage condition representing an equilibrium state under which investors compare interest rates available on bank deposits in two countries. [1] The fact that this condition does not always hold allows for potential opportunities to earn riskless profits from covered interest arbitrage. Two assumptions central to interest rate parity are capital mobility and perfect substitutability of domestic and foreign assets. Given foreign exchange market equilibrium, the interest rate parity condition implies that the expected return on domestic assets will equal the exchange rate-adjusted expected return on foreign currency assets. Investors then cannot earn arbitrage profits by borrowing in a country with a lower interest rate, exchanging for foreign currency, and investing in a foreign country with a higher interest rate, due to gains or losses from exchanging back to their domestic currency at maturity. [2] Interest rate parity takes on two distinctive forms: uncovered interest rate parity refers to the parity condition in which exposure to foreign exchange risk (unanticipated changes in exchange rates) is uninhibited, whereas covered interest rate parity refers to the condition in which a forward contract has been used to cover (eliminate exposure to) exchange rate risk. Each form of the parity condition demonstrates a unique relationship with implications for the forecasting of future exchange rates: the forward exchange rate and the future spot exchange rate. [1]
Economists have found empirical evidence that covered interest rate parity generally holds, though not with precision due to the effects of various risks, costs, taxation, and ultimate differences in liquidity. When both covered and uncovered interest rate parity hold, they expose a relationship suggesting that the forward rate is an unbiased predictor of the future spot rate. This relationship can be employed to test whether uncovered interest rate parity holds, for which economists have found mixed results. When uncovered interest rate parity and purchasing power parity hold together, they illuminate a relationship named real interest rate parity, which suggests that expected real interest rates represent expected adjustments in the real exchange rate. This relationship generally holds strongly over longer terms and among emerging market countries.
Interest rate parity rests on certain assumptions, the first being that capital is mobile - investors can readily exchange domestic assets for foreign assets. The second assumption is that assets have perfect substitutability, following from their similarities in riskiness and liquidity. Given capital mobility and perfect substitutability, investors would be expected to hold those assets offering greater returns, be they domestic or foreign assets. However, both domestic and foreign assets are held by investors. Therefore, it must be true that no difference can exist between the returns on domestic assets and the returns on foreign assets. [2] That is not to say that domestic investors and foreign investors will earn equivalent returns, but that a single investor on any given side would expect to earn equivalent returns from either investment decision. [3]
When the no-arbitrage condition is satisfied without the use of a forward contract to hedge against exposure to exchange rate risk, interest rate parity is said to be uncovered. Risk-neutral investors will be indifferent among the available interest rates in two countries because the exchange rate between those countries is expected to adjust such that the dollar return on dollar deposits is equal to the dollar return on euro deposits, thereby eliminating the potential for uncovered interest arbitrage profits. Uncovered interest rate parity helps explain the determination of the spot exchange rate. The following equation represents uncovered interest rate parity. [1]
where
The dollar return on dollar deposits, , is shown to be equal to the dollar return on euro deposits, .
Uncovered interest rate parity asserts that an investor with dollar deposits will earn the interest rate available on dollar deposits, while an investor holding euro deposits will earn the interest rate available in the eurozone, but also a potential gain or loss on euros depending on the rate of appreciation or depreciation of the euro against the dollar. Economists have extrapolated a useful approximation of uncovered interest rate parity that follows intuitively from these assumptions. If uncovered interest rate parity holds, such that an investor is indifferent between dollar versus euro deposits, then any excess return on euro deposits must be offset by some expected loss from depreciation of the euro against the dollar. Conversely, some shortfall in return on euro deposits must be offset by some expected gain from appreciation of the euro against the dollar. The following equation represents the uncovered interest rate parity approximation. [1]
where
A more universal way of stating the approximation is "the home interest rate equals the foreign interest rate plus the expected rate of depreciation of the home currency." [1]
When the no-arbitrage condition is satisfied with the use of a forward contract to hedge against exposure to exchange rate risk, interest rate parity is said to be covered. Investors will still be indifferent among the available interest rates in two countries because the forward exchange rate sustains equilibrium such that the dollar return on dollar deposits is equal to the dollar return on foreign deposit, thereby eliminating the potential for covered interest arbitrage profits. Furthermore, covered interest rate parity helps explain the determination of the forward exchange rate. The following equation represents covered interest rate parity. [1] [4]
where
The dollar return on dollar deposits, , is shown to be equal to the dollar return on euro deposits, .
Traditionally, covered interest rate parity (CIRP) was found to hold when there is open capital mobility and limited capital controls, and this finding is confirmed for all currencies freely traded in the present day. One such example is when the United Kingdom and Germany abolished capital controls between 1979 and 1981. Maurice Obstfeld and Alan Taylor calculated hypothetical profits as implied by the expression of a potential inequality in the CIRP equation (meaning a difference in returns on domestic versus foreign assets) during the 1960s and 1970s, which would have constituted arbitrage opportunities if not for the prevalence of capital controls. However, given financial liberalization and resulting capital mobility, arbitrage temporarily became possible until equilibrium was restored. Since the abolition of capital controls in the United Kingdom and Germany, potential arbitrage profits have been near zero. Factoring in transaction costs arising from fees and other regulations, arbitrage opportunities are fleeting or nonexistent when such costs exceed deviations from parity. [1] [5] While CIRP generally holds, it does not hold with precision due to the presence of transaction costs, political risks, tax implications for interest earnings versus gains from foreign exchange, and differences in the liquidity of domestic versus foreign assets. [5] [6] [7]
Researchers found evidence that significant deviations from CIRP during the onset of the 2007–2008 financial crisis were driven by concerns over risk posed by counter parties to banks and financial institutions in Europe and the US in the foreign exchange swap market. The European Central Bank's efforts to provide US dollar liquidity in the foreign exchange swap market, along with similar efforts by the Federal Reserve, had a moderating impact on CIRP deviations between the dollar and the euro. Such a scenario was found to be reminiscent of deviations from CIRP during the 1990s driven by struggling Japanese banks which looked toward foreign exchange swap markets to try and acquire dollars to bolster their creditworthiness. [8] A second period of deviations from CIRP after 2012, at a time of relatively calm markets, led to renewed debate about the extent and origin of deviations from CIRP. Explanations include intermediary constraints that can lead to limits to arbitrage, such as balance sheet costs of arbitrage, raised by a team of researchers at the Bank for International Settlements. [9] Other explanations question common assumptions underlying the CIRP condition, such as the choice of discount factors. Deviations from CIRP remain subject to ongoing debate.
When both covered and uncovered interest rate parity (UIRP) hold, such a condition sheds light on a noteworthy relationship between the forward and expected future spot exchange rates, as demonstrated below.
Dividing the equation for UIRP by the equation for CIRP yields the following equation:
which can be rewritten as:
This equation represents the unbiasedness hypothesis, which states that the forward exchange rate is an unbiased predictor of the future spot exchange rate. [10] [11] Given strong evidence that CIRP holds, the forward rate unbiasedness hypothesis can serve as a test to determine whether UIRP holds (in order for the forward rate and expected spot rate to be equal, both CIRP and UIRP conditions must hold). Evidence for the validity and accuracy of the unbiasedness hypothesis, particularly evidence for cointegration between the forward rate and future spot rate, is mixed as researchers have published numerous papers demonstrating both empirical support and empirical failure of the hypothesis. [10]
UIRP is found to have some empirical support in tests for correlation between expected rates of currency depreciation and the forward premium or discount. [1] Evidence suggests that whether UIRP holds depends on the currency examined, and deviations from UIRP have been found to be less substantial when examining longer time horizons. [12] Some studies of monetary policy have offered explanations for why UIRP fails empirically. Researchers demonstrated that if a central bank manages interest rate spreads in strong response to the previous period's spreads, that interest rate spreads had negative coefficients in regression tests of UIRP. Another study which set up a model wherein the central bank's monetary policy responds to exogenous shocks, that the central bank's smoothing of interest rates can explain empirical failures of UIRP. [13]
A study of central bank interventions on the US dollar and Deutsche mark found only limited evidence of any substantial effect on deviations from UIRP. [14] UIRP has been found to hold over very small spans of time (covering only a number of hours) with a high frequency of bilateral exchange rate data. [15] Tests of UIRP for economies experiencing institutional regime changes, using monthly exchange rate data for the US dollar versus the Deutsche mark and the Spanish peseta versus the British pound, have found some evidence that UIRP held when US and German regime changes were volatile, and held between Spain and the United Kingdom particularly after Spain joined the European Union in 1986 and began liberalizing capital mobility. [16]
When both UIRP (particularly in its approximation form) and purchasing power parity (PPP) hold, the two parity conditions together reveal a relationship among expected real interest rates, wherein changes in expected real interest rates reflect expected changes in the real exchange rate. This condition is known as real interest rate parity (RIRP) and is related to the international Fisher effect. [17] [18] [19] [20] [21] The following equations demonstrate how to derive the RIRP equation.
where
If the above conditions hold, then they can be combined and rearranged as the following:
RIRP rests on several assumptions, including efficient markets, no country risk premia, and zero change in the expected real exchange rate. The parity condition suggests that real interest rates will equalize between countries and that capital mobility will result in capital flows that eliminate opportunities for arbitrage. There exists strong evidence that RIRP holds tightly among emerging markets in Asia and also Japan. The half-life period of deviations from RIRP have been examined by researchers and found to be roughly six or seven months, but between two and three months for certain countries. Such variation in the half-lives of deviations may be reflective of differences in the degree of financial integration among the country groups analyzed. [22] RIRP does not hold over short time horizons, but empirical evidence has demonstrated that it generally holds well across long time horizons of five to ten years. [23]
In economics and finance, arbitrage is the practice of taking advantage of a difference in prices in two or more markets – striking a combination of matching deals to capitalize on the difference, the profit being the difference between the market prices at which the unit is traded. When used by academics, an arbitrage is a transaction that involves no negative cash flow at any probabilistic or temporal state and a positive cash flow in at least one state; in simple terms, it is the possibility of a risk-free profit after transaction costs. For example, an arbitrage opportunity is present when there is the possibility to instantaneously buy something for a low price and sell it for a higher price.
The Black–Scholes or Black–Scholes–Merton model is a mathematical model for the dynamics of a financial market containing derivative investment instruments. From the parabolic partial differential equation in the model, known as the Black–Scholes equation, one can deduce the Black–Scholes formula, which gives a theoretical estimate of the price of European-style options and shows that the option has a unique price given the risk of the security and its expected return. The equation and model are named after economists Fischer Black and Myron Scholes. Robert C. Merton, who first wrote an academic paper on the subject, is sometimes also credited.
In finance, an exchange rate is the rate at which one currency will be exchanged for another currency. Currencies are most commonly national currencies, but may be sub-national as in the case of Hong Kong or supra-national as in the case of the euro.
In financial mathematics, the put–call parity defines a relationship between the price of a European call option and European put option, both with the identical strike price and expiry, namely that a portfolio of a long call option and a short put option is equivalent to a single forward contract at this strike price and expiry. This is because if the price at expiry is above the strike price, the call will be exercised, while if it is below, the put will be exercised, and thus in either case one unit of the asset will be purchased for the strike price, exactly as in a forward contract.
In finance, a futures contract is a standardized legal contract to buy or sell something at a predetermined price for delivery at a specified time in the future, between parties not yet known to each other. The asset transacted is usually a commodity or financial instrument. The predetermined price of the contract is known as the forward price or delivery price. The specified time in the future when delivery and payment occur is known as the delivery date. Because it derives its value from the value of the underlying asset, a futures contract is a derivative.
In finance, a forward contract, or simply a forward, is a non-standardized contract between two parties to buy or sell an asset at a specified future time at a price agreed on in the contract, making it a type of derivative instrument. The party agreeing to buy the underlying asset in the future assumes a long position, and the party agreeing to sell the asset in the future assumes a short position. The price agreed upon is called the delivery price, which is equal to the forward price at the time the contract is entered into.
In finance, a swap is an agreement between two counterparties to exchange financial instruments, cashflows, or payments for a certain time. The instruments can be almost anything but most swaps involve cash based on a notional principal amount.
Rational pricing is the assumption in financial economics that asset prices – and hence asset pricing models – will reflect the arbitrage-free price of the asset as any deviation from this price will be "arbitraged away". This assumption is useful in pricing fixed income securities, particularly bonds, and is fundamental to the pricing of derivative instruments.
In finance, a foreign exchange option is a derivative financial instrument that gives the right but not the obligation to exchange money denominated in one currency into another currency at a pre-agreed exchange rate on a specified date. See Foreign exchange derivative.
Triangular arbitrage is the act of exploiting an arbitrage opportunity resulting from a pricing discrepancy among three different currencies in the foreign exchange market. A triangular arbitrage strategy involves three trades, exchanging the initial currency for a second, the second currency for a third, and the third currency for the initial. During the second trade, the arbitrageur locks in a zero-risk profit from the discrepancy that exists when the market cross exchange rate is not aligned with the implicit cross exchange rate. A profitable trade is only possible if there exist market imperfections. Profitable triangular arbitrage is very rarely possible because when such opportunities arise, traders execute trades that take advantage of the imperfections and prices adjust up or down until the opportunity disappears.
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 exchange rate risk. Using forward contracts enables arbitrageurs such as individual investors or banks to make use of the forward premium 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.
The cost of carry or carrying charge is the cost of holding a security or a physical commodity over a period of time. The carrying charge includes insurance, storage and interest on the invested funds as well as other incidental costs. In interest rate futures markets, it refers to the differential between the yield on a cash instrument and the cost of the funds necessary to buy the instrument.
Uncovered interest arbitrage is an arbitrage trading strategy whereby an investor capitalizes on the interest rate differential between two countries. Unlike covered interest arbitrage, uncovered interest arbitrage involves no hedging of foreign exchange risk with the use of forward contracts or any other contract. The strategy involves risk, as an investor exposed to exchange rate fluctuations is speculating that exchange rates will remain favorable enough for arbitrage to be profitable. The opportunity to earn profits arises from the reality that the uncovered interest rate parity condition does not constantly hold—that is, the interest rate on investments in one country's currency does not always equal the interest rate on foreign-currency investments plus the rate of appreciation that is expected for the foreign currency relative to the domestic currency. When a discrepancy between these occurs, investors who are willing to take on risk will not be indifferent between the two possible locations of investment, and will invest in whichever currency is expected to offer a higher rate of return including currency exchange gains or losses.
The overshooting model, or the exchange rate overshoot hypothesis, first developed by economist Rudi Dornbusch, is a theoretical explanation for high levels of exchange rate volatility. The key features of the model include the assumptions that goods' prices are sticky, or slow to change, in the short run, but the prices of currencies are flexible, that arbitrage in asset markets holds, via the uncovered interest parity equation, and that expectations of exchange rate changes are "consistent": that is, rational. The most important insight of the model is that adjustment lags in some parts of the economy can induce compensating volatility in others; specifically, when an exogenous variable changes, the short-term effect on the exchange rate can be greater than the long-run effect, so in the short term, the exchange rate overshoots its new equilibrium long-term value.
The forward exchange rate is the exchange rate at which a bank agrees to exchange one currency for another at a future date when it enters into a forward contract with an investor. Multinational corporations, banks, and other financial institutions enter into forward contracts to take advantage of the forward rate for hedging purposes. The forward exchange rate is determined by a parity relationship among the spot exchange rate and differences in interest rates between two countries, which reflects an economic equilibrium in the foreign exchange market under which arbitrage opportunities are eliminated. When in equilibrium, and when interest rates vary across two countries, the parity condition implies that the forward rate includes a premium or discount reflecting the interest rate differential. Forward exchange rates have important theoretical implications for forecasting future spot exchange rates. Financial economists have put forth a hypothesis that the forward rate accurately predicts the future spot rate, for which empirical evidence is mixed.
In options trading, a box spread is a combination of positions that has a certain payoff, considered to be simply "delta neutral interest rate position". For example, a bull spread constructed from calls combined with a bear spread constructed from puts has a constant payoff of the difference in exercise prices assuming that the underlying stock does not go ex-dividend before the expiration of the options. If the underlying asset has a dividend of X, then the settled value of the box will be 10 + x. Under the no-arbitrage assumption, the net premium paid out to acquire this position should be equal to the present value of the payoff.
The following outline is provided as an overview of and topical guide to finance:
The international Fisher effect is a hypothesis in international finance that suggests differences in nominal interest rates reflect expected changes in the spot exchange rate between countries. The hypothesis specifically states that a spot exchange rate is expected to change equally in the opposite direction of the interest rate differential; thus, the currency of the country with the higher nominal interest rate is expected to depreciate against the currency of the country with the lower nominal interest rate, as higher nominal interest rates reflect an expectation of inflation.
The carry of an asset is the return obtained from holding it, or the cost of holding it. For instance, commodities are usually negative carry assets, as they incur storage costs or may suffer from depreciation. But in some circumstances, appropriately hedged commodities can be positive carry assets if the forward/futures market is willing to pay sufficient premium for future delivery. This can also refer to a trade with more than one leg, where you earn the spread between borrowing a low carry asset and lending a high carry one; such as gold during financial crisis, due to its safe haven quality.
Spot–future parity is a parity condition whereby, if an asset can be purchased today and held until the exercise of a futures contract, the value of the future should equal the current spot price adjusted for the cost of money, dividends, "convenience yield" and any carrying costs. That is, if a person can purchase a good for price S and conclude a contract to sell it one month later at a price of F, the price difference should be no greater than the cost of using money less any expenses from holding the asset; if the difference is greater, the person has an opportunity to buy and sell the "spots" and "futures" for a risk-free profit, i.e. an arbitrage. Spot–future parity is an application of the law of one price; see also Rational pricing and #Futures.