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Purchasing power parity

Purchasing power parity

A popular metric used by macroeconomic analysts that compares different countries' currencies through a "basket of goods" approach

Purchase power parity (PPP) is an economic theory that allows for the comparison of the purchasing power of various world currencies to one another. It is the theoretical exchange rate at which you can buy the same amount of goods and services with another currency.

The basis for PPP is the "law of one price". In the absence of transportation and other transaction costs, competitive markets will equalize the price of an identical good in two countries when the prices are expressed in the same currency. For example, a particular TV set that sells for 750 Canadian Dollars [CAD] in Vancouver should cost 500 US Dollars [USD] in Seattle when the exchange rate between Canada and the US is 1.50 CAD/USD. If the price of the TV in Vancouver was only 700 CAD, consumers in Seattle would prefer buying the TV set in Vancouver.

If this process (called "arbitrage") is carried out at a large scale, the US consumers buying Canadian goods will bid up the value of the Canadian Dollar, thus making Canadian goods more costly to them. This process continues until the goods have again the same price. There are three caveats with this law of one price. (1) As mentioned above, transportation costs, barriers to trade, and other transaction costs, can be significant. (2) There must be competitive markets for the goods and services in both countries. (3) The law of one price only applies to tradeable goods; immobile goods such as houses, and many services that are local, are of course not traded between countries.

Economists use two versions of Purchasing Power Parity: absolute PPP and relative PPP. Absolute PPP was described in the previous paragraph; it refers to the equalization of price levels across countries. Put formally, the exchange rate between Canada and the United States ECAD/USD is equal to the price level in Canada PCAN divided by the price level in the United States PUSA. Assume that the price level ratio PCAD/PUSD implies a PPP exchange rate of 1.3 CAD per 1 USD. If today's exchange rate ECAD/USD is 1.5 CAD per 1 USD, PPP theory implies that the CAD will appreciate (get stronger) against the USD, and the USD will in turn depreciate (get weaker) against the CAD.

Relative PPP refers to rates of changes of price levels, that is, inflation rates. This proposition states that the rate of appreciation of a currency is equal to the difference in inflation rates between the foreign and the home country. For example, if Canada has an inflation rate of 1% and the US has an inflation rate of 3%, the US Dollar will depreciate against the Canadian Dollar by 2% per year. This proposition holds well empirically especially when the inflation differences are large.

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Further Resources

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Conversion rates - Purchasing power parities (PPP) - OECD Data

Web

Purchasing Power Parity

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Purchasing Power Parity

Web

April 22, 2017

Purchasing Power Parity

Web

August 28, 2014

Purchasing Power Parity (PPP)

Web

May 19, 2014

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