There is a great deal of academic theory revolving around currencies. While often not applicable directly to day-to-day trading, it is helpful to understand the overarching ideas behind the academic research.

The main economic theories found in the foreign exchange deal with parity conditions. A parity condition is an economic explanation of the price at which two currencies should be exchanged, based on factors such as inflation and interest rates. The economic theories suggest that when the parity condition does not hold, an arbitrage opportunity exists for market participants. However, arbitrage opportunities, as in many other markets, are quickly discovered and eliminated before even giving the individual investor an opportunity to capitalize on them. Other theories are based on economic factors such as trade, capital flows and the way a country runs its operations. We review each of them briefly below.

Major Theories: Purchasing Power Parity
Purchasing Power Parity (PPP) is the economic theory that price levels between two countries should be equivalent to one another after exchange-rate adjustment. The basis of this theory is the law of one price, where the cost of an identical good should be the same around the world. Based on the theory, if there is a large difference in price between two countries for the same product after exchange rate adjustment, an arbitrage opportunity is created, because the product can be obtained from the country that sells it for the lowest price.

The relative version of PPP is as follows:

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Where ‘e’ represents the rate of change in the exchange rate and ‘د€₁‘ and ‘د€₂‘represent the rates of inflation for country 1 and country 2, respectively.

For example, if the inflation rate for country XYZ is 10% and the inflation for country ABC is 5%, then ABC’s currency should appreciate 4.76% against that of XYZ.

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Interest Rate Parity
The concept of Interest Rate Parity (IRP) is similar to PPP, in that it suggests that for there to be no arbitrage opportunities, two assets in two different countries should have similar interest rates, as long as the risk for each is the same. The basis for this parity is also the law of one price, in that the purchase of one investment asset in one country should yield the same return as the exact same asset in another country; otherwise exchange rates would have to adjust to make up for the difference.

The formula for determining IRP can be found by:

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Where ‘F’ represents the forward exchange rate; ‘S’ represents the spot exchange rate; ‘i₁‘ represents the interest rate in country 1; and ‘i₂‘ represents the interest rate in country 2.

International Fisher Effect
The International Fisher Effect (IFE) theory suggests that the exchange rate between two countries should change by an amount similar to the difference between their nominal interest rates. If the nominal rate in one country is lower than another, the currency of the country with the lower nominal rate should appreciate against the higher rate country by the same amount.

The formula for IFE is as follows:

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Where ‘e’ represents the rate of change in the exchange rate and ‘i₁‘ and ‘i₂‘represent the rates of inflation for country 1 and country 2, respectively.

Balance of Payments Theory
A country’s balance of payments is comprised of two segments – the current account and the capital account – which measure the inflows and outflows of goods and capital for a country. The balance of payments theory looks at the current account, which is the account dealing with trade of tangible goods, to get an idea of exchange-rate directions.

If a country is running a large current account surplus or deficit, it is a sign that a country’s exchange rate is out of equilibrium. To bring the current account back into equilibrium, the exchange rate will need to adjust over time. If a country is running a large deficit (more imports than exports), the domestic currency will depreciate. On the other hand, a surplus would lead to currency appreciation.

The balance of payments identity is found by:

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Where BCA represents the current account balance; BKA represents the capital account balance; and BRA represents the reserves account balance.

Real Interest Rate Differentiation Model
The Real Interest Rate Differential Model simply suggests that countries with higher real interest rates will see their currencies appreciate against countries with lower interest rates. The reason for this is that investors around the world will move their money to countries with higher real rates to earn higher returns, which bids up the price of the higher real rate currency.

Asset Market Model
The Asset Market Model looks at the inflow of money into a country by foreign investors for the purpose of purchasing assets such as stocks, bonds and other financial instruments. If a country is seeing large inflows by foreign investors, the price of its currency is expected to increase, as the domestic currency needs to be purchased by these foreign investors. This theory considers the capital account of the balance of trade compared to the current account in the prior theory. This model has gained more acceptance as the capital accounts of countries are starting to greatly outpace the current account as international money flow increases.

Monetary Model
The Monetary Model focuses on a country’s monetary policy to help determine the exchange rate. A country’s monetary policy deals with the money supply of that country, which is determined by both the interest rate set by central banks and the amount of money printed by the treasury. Countries that adopt a monetary policy that rapidly grows its monetary supply will see inflationary pressure due to the increased amount of money in circulation. This leads to a devaluation of the currency.

These economic theories, which are based on assumptions and perfect situations, help to illustrate the basic fundamentals of currencies and how they are impacted by economic factors. However, the fact that there are so many conflicting theories indicates the difficulty in any one of them being 100% accurate in predicting currency fluctuations. Their importance will likely vary by the different market environment, but it is still important to know the fundamental basis behind each of the theories.

Economic Data
Economic theories may move currencies in the long term, but on a shorter-term, day-to-day or week-to-week basis, economic data has a more significant impact. It is often said the biggest companies in the world are actually countries and that their currency is essentially shares in that country. Economic data, such as the latest gross domestic product (GDP) numbers, are often considered to be like a company’s latest earnings data. In the same way that financial news and current events can affect a company’s stock price, news and information about a country can have a major impact on the direction of that country’s currency. Changes in interest rates, inflation, unemployment, consumer confidence, GDP, political stability etc. can all lead to extremely large gains/losses depending on the nature of the announcement and the current state of the country.

The number of economic announcements made each day from around the world can be intimidating, but as one spends more time learning about the forex market it becomes clear which announcements have the greatest influence. Listed below are a number of economic indicators that are generally considered to have the greatest influence – regardless of which country the announcement comes from.

Employment Data
Most countries release data about the number of people that currently are employed within that economy. In the U.S., this data is known as non-farm payrolls and is released the first Friday of the month by the Bureau of Labor Statistics. In most cases, strong increases in employment signal that a country enjoys a prosperous economy, while decreases are a sign of potential contraction. If a country has gone recently through economic troubles, strong employment data could send the currency higher because it is a sign of economic health and recovery. On the other hand, high employment can also lead to inflation, so this data could send the currency downward. In other words, economic data and the movement of currency will often depend on the circumstances that exist when the data is released.

Interest Rates
As was seen with some of the economic theories, interest rates are a major focus in the forex market. The most focus by market participants, in terms of interest rates, is placed on the country’s central bank changes of its bank rate, which is used to adjust monetary supply and institute the country’s monetary policy. In the U.S., the Federal Open Market Committee (FOMC) determines the bank rate, or the rate at which commercial banks can borrow and lend to the U.S. Treasury. The FOMC meets eight times a year to make decisions on whether to raise, lower or leave the bank rate the same; and each meeting, along with the minutes, is a point of focus. (For more on central banks read Get to Know the Major Central Banks.)

Inflation
Inflation data measures the increases and decreases of price levels over a period of time. Due to the sheer amount of goods and services within an economy, a basket of goods and services is used to measure changes in prices. Price increases are a sign of inflation, which suggests that the country will see its currency depreciate. In the U.S., inflation data is shown in the Consumer Price Index, which is released on a monthly basis by the Bureau of Labor Statistics.

Gross Domestic Product
The gross domestic product of a country is a measure of all of the finished goods and services that a country generated during a given period. The GDP calculation is split into four categories: private consumption, government spending, business spending and total net exports. GDP is considered the best overall measure of the health of a country’s economy, with GDP increases signaling economic growth. The healthier a country’s economy is, the more attractive it is to foreign investors, which in turn can often lead to increases in the value of its currency, as money moves into the country. In the U.S., this data is released by the Bureau of Economic Analysis once a month in the third or fourth quarter of the month.

Retail Sales
Retail sales data measures the amount of sales that retailers make during the period, reflecting consumer spending. The measure itself doesn’t look at all stores, but, similar to GDP, uses a group of stores of varying types to get an idea of consumer spending. This measure also gives market participants an idea of the strength of the economy, where increased spending signals a strong economy. In the U.S., the Department of Commerce releases data on retail sales around the middle of the month.

Durable Goods
The data for durable goods (those with a lifespan of more than three years) measures the amount of manufactured goods that are ordered, shipped and unfilled for the time period. These goods include such things as cars and appliances, giving economists an idea of the amount of individual spending on these longer-term goods, along with an idea of the health of the factory sector. This measure again gives market participants insight into the health of the economy, with data being released around the 26th of the month by the Department of Commerce.

Trade and Capital Flows
Interactions between countries create huge monetary flows that can have a substantial impact on the value of currencies. As was mentioned before, a country that imports far more than it exports could see its currency decline due to its need to sell its own currency to purchase the currency of the exporting nation. Furthermore, increased investments in a country can lead to substantial increases in the value of its currency.

Trade flow data looks at the difference between a country’s imports and exports, with a trade deficit occurring when imports are greater than exports. In the U.S., the Commerce Department releases balance of trade data on a monthly basis, which shows the amount of goods and services that the U.S. exported and imported during the past month. Capital flow data looks at the difference in the amount of currency being brought in through investment and/or exports to currency being sold for foreign investments and/or imports. A country that is seeing a lot of foreign investment, where outsiders are purchasing domestic assets such as stocks or real estate, will generally have a capital flow surplus.

Balance of payments data is the combined total of a country’s trade and capital flow over a period of time. The balance of payments is split into three categories: the current account, the capital account and the financial account. The current account looks at the flow of goods and services between countries. The capital account looks at the exchange of money between countries for the purpose of purchasing capital assets. The financial account looks at the monetary flow between countries for investment purposes.

Macroeconomic and Geopolitical Events
The biggest changes in the forex often come from macroeconomic and geopolitical events such as wars, elections, monetary policy changes and financial crises. These events have the ability to change or reshape the country, including its fundamentals. For example, wars can put a huge economic strain on a country and greatly increase the volatility in a region, which could impact the value of its currency. It is important to keep up to date on these macroeconomic and geopolitical events.