What Is Purchasing Power Parity (PPP), and How Is It Calculated?

One popular macroeconomic analysis metric to compare economic productivity and standards of living between countries is purchasing power parity (PPP). PPP is an economic theory that compares different countries' currencies through a "basket of goods" approach, not to be confused with the Paycheck Protection Program created by the CARES Act.

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According to this concept, two currencies are in equilibrium—known as the currencies being at par—when a basket of goods is priced the same in both countries, taking into account the exchange rates.

Key Takeaways

  • Purchasing power parity (PPP) is a popular metric used by macroeconomic analysts that compares different countries' currencies through a "basket of goods" approach.
  • Purchasing power parity (PPP) allows for economists to compare economic productivity and standards of living between countries.
  • Some countries adjust their gross domestic product (GDP) figures to reflect PPP.

Click Play to Learn How to Calculate Purchasing Power Parity

Calculating Purchasing Power Parity

The relative version of PPP is calculated with the following formula:

 S = P 1 P 2 where: S =  Exchange rate of currency  1  to currency  2 P 1 =  Cost of good  X  in currency  1 \begin{aligned} &S=\frac{P_1}{P_2}\\ &\textbf{where:}\\ &S=\text{ Exchange rate of currency }1\text{ to currency }2\\ &P_1=\text{ Cost of good }X\text{ in currency }1\\ &P_2=\text{ Cost of good }X\text{ in currency }2 \end{aligned} S=P2P1where:S= Exchange rate of currency 1 to currency 2P1= Cost of good X in currency 1

Comparing Nations' Purchasing Power Parity

To make a meaningful comparison of prices across countries, a wide range of goods and services must be considered. However, this one-to-one comparison is difficult to achieve due to the sheer amount of data that must be collected and the complexity of the comparisons that must be drawn. To help facilitate this comparison, the University of Pennsylvania and the United Nations joined forces to establish the International Comparison Program (ICP) in 1968.

With this program, the PPPs generated by the ICP have a basis from a worldwide price survey that compares the prices of hundreds of various goods and services. The program helps international macroeconomists estimate global productivity and growth.

Every few years, the World Bank releases a report that compares the productivity and growth of various countries in terms of PPP and U.S. dollars. Both the International Monetary Fund (IMF) and the Organization for Economic Cooperation and Development (OECD) use weights based on PPP metrics to make predictions and recommend economic policy. The recommended economic policies can have an immediate short-term impact on financial markets.

Also, some forex traders use PPP to find potentially overvalued or undervalued currencies. Investors who hold stock or bonds of foreign companies may use the survey's PPP figures to predict the impact of exchange-rate fluctuations on a country's economy, and thus the impact on their investment.

Pairing Purchasing Power Parity With Gross Domestic Product

In contemporary macroeconomics, gross domestic product (GDP) refers to the total monetary value of the goods and services produced within one country. Nominal GDP calculates the monetary value in current, absolute terms. Real GDP adjusts the nominal gross domestic product for inflation.

However, some accounting goes even further, adjusting GDP for the PPP value. This adjustment attempts to convert nominal GDP into a number more easily comparable between countries with different currencies.

To better understand how GDP paired with purchase power parity works, suppose it costs $10 to buy a shirt in the U.S., and it costs €8.00 to buy an identical shirt in Germany. To make an apples-to-apples comparison, we must first convert the €8.00 into U.S. dollars. If the exchange rate was such that the shirt in Germany costs $15.00, the PPP would, therefore, be 15/10, or 1.5.

In other words, for every $1.00 spent on the shirt in the U.S., it takes $1.50 to obtain the same shirt in Germany buying it with the euro.

GDP by Purchasing Power Parity vs Nominal GDP

Drawbacks of Purchasing Power Parity

Since 1986, The Economist has playfully tracked the price of McDonald's Corp.’s (MCD) Big Mac hamburger across many countries. Their study results in the famed "Big Mac Index". In "Burgernomics"—a prominent 2003 paper that explores the Big Mac Index and PPP—authors Michael R. Pakko and Patricia S. Pollard cited the following factors to explain why the purchasing power parity theory is not a good reflection of reality.

Transport Costs

Goods that are unavailable locally must be imported, resulting in transport costs. These costs include not only fuel but import duties as well. Imported goods will consequently sell at a relatively higher price than do identical locally sourced goods.

Tax Differences

Government sales taxes such as the value-added tax (VAT) can spike prices in one country, relative to another.

Government Intervention

Tariffs can dramatically augment the price of imported goods, where the same products in other countries will be comparatively cheaper.

Non-Traded Services

The Big Mac's price factors input costs that are not traded. These factors include such items as insurance, utility costs, and labor costs. Therefore, those expenses are unlikely to be at parity internationally.

Market Competition

Goods might be deliberately priced higher in a country. In some cases, higher prices are because a company may have a competitive advantage over other sellers. The company may have a monopoly or be part of a cartel of companies that manipulate prices, keeping them artificially high.

The Bottom Line

While it's not a perfect measurement metric, purchase power parity does allow for the possibility of comparing pricing between countries that have differing currencies.

Article Sources
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  2. World Bank. "International Comparison Program (ICP): History."

  3. World Bank. "International Comparison Program (ICP): Uses."

  4. World Bank. "International Comparison Program (ICP): Overview."

  5. World Bank. "Who uses PPPs – Examples of Uses by International Organizations."

  6. St. Louis Federal Reserve Bank. "Burgernomics: A Big Mac Guide to Purchasing Power Parity," Page 1.

  7. St. Louis Federal Reserve Bank. "Burgernomics: A Big Mac Guide to Purchasing Power Parity," Pages 16-17.

  8. St. Louis Federal Reserve Bank. "Burgernomics: A Big Mac Guide to Purchasing Power Parity," Page 21.