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Forex 101

What is Interest Rate Parity?

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As you become more and more involved in the forex market, you will realize that there are a wide number of factors which can influence the exchange rates at any one time. This can include an array of both internal, and external factors. One of the biggest factors in determining currency exchange rates, is the interest rate of a country. The two are interwoven and looking at the difference between the interest rates of two countries, can even help you plot the future course of the exchange rate. This is according to the theory of interest rate parity which we will explain and examine in further detail here.

What is Interest Rate Parity?

At the most basic of levels, what interest rate parity means is that you should not be in a situation where you can benefit more from exchanging money in one country and investing it in another, than you would from earning that money and investing it in your own country and then converting the profits to the other currency.

Before looking at an example to illustrate this point, it is important to note that the forward exchange rate is integral to the theory of interest rate parity, so let’s quickly recap the difference between the spot rate, and the forward rate, in forex trading.

Spot Rate: This is the current exchange rate for a currency if you are trading right now on the forex market. As a regular forex trader, this is the rate you will almost always see posted by your broker.

Forward Rate: This is the rate that a bank or other party to the agreement agrees to pay for a currency at a certain time in the future. This is the rate you will also see if you are trading in forex futures.

Interest Rate Parity Example

The forward rate is important when we are talking about the theory of interest rate parity. As a very simplified example, you should not benefit from exchanging US Dollars to Euros and then investing it in Europe, and exchanging it back to Dollars, more than you would from investing the money in the US and then exchanging the resulting profits to Euro.

Detailing the example further, presuming that the spot rate is €0.75 for every dollar, you will receive €7,500 for a $10,000 exchange. Also presuming the interest rate In Europe is 3%, your return after 1 year would be €7,720.

Now, if you were to keep this money invested in the US at a higher interest rate, then exchange your return to Euro at the end of one year, you would be availing of the forward rate. This would, according to the theory of interest rate parity, net you the same result of €7,720 when the formula is applied.

In essence, what the theory, and example should demonstrate is that the interest rate difference between two countries, should also match the difference between the spot and forward currency exchange rate.

Covered or Uncovered Interest Rate Parity

When we talk about interest rate parity, we can actually divide it into two different types. These are covered interest parity, and uncovered interest parity. In the most simple of terms, covered interest parity is said to exist when there is a forward contract in place which has locked in the forward interest rate. This should leave no room for any difference at all between what is contracted, and what actually happens.

Uncovered interest rate parity is exactly the opposite in that there are typically no contracts in place here to lock in the forward interest rate. The parity in this case is simply based on the expected spot rate in the future. With this, there may be room for error and possibly a slight difference between the result of the formula, and the actual outcome. With that said though, forecasts on spots rates in the future tend to be quite accurate.

Why is Interest Rate Parity Important?

There are a couple of key reasons why interest rate parity is important. The first of these is to stop actions like arbitrage happening on a large scale. Now, this kind of thing does certainly still occur, but the scope for it to happen is greatly tightened. This is the simultaneous purchase and sale of currency or assets in two different markets or areas, exploiting a short-term difference.

More broadly speaking, it prevents not only retail, but also more powerful traders from exploiting gaps in the market which would leave them with a guaranteed, no-risk return. In the bigger picture, what this would do is actually remove the integrity from the forex market and others in entire countries or regions. A by-product of this would be that as traders moved to exploit these gaps, there would be huge and volatile swings in the market. Interest rate parity provides for a degree of assurance that this will not happen, and thus a stability that traders can rely on.

There are still some situations in which the theory of interest rate parity can be challenged. These include in certain arbitrage situations particularly as technology and algorithmic forex trading continue to advance, and the carry trade has long posed a challenge to the formula of interest rate parity, though this can be mitigated depending on if it is covered, or uncovered.

Final Thoughts

The concept and formula behind interest rate parity can be one which many in forex trading, even those with more experience, find to be complex. This is true at least at face value. With a pragmatic approach though, it becomes clear that the core of the concept is relatively simple, and it can even help you to accurately forecast future currency rates if correctly applied. If you are getting involved in more complex trading situations, particularly involving multiple currencies, and regions, having the formula, and a clear understanding of the concept of interest rate parity becomes essential to reaching your forex trading goals.

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Anthony is a financial journalist and business advisor with several years’ experience writing for some of the most well-known sites in the Forex world. A keen trader turned industry writer, he is currently based in Shanghai with a finger on the pulse of Asia’s biggest markets.

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