Paritáselméletek

Paritáselméletek, in English known as parity theories or parity principles, are a set of economic theories that aim to explain the long-term exchange rate between two countries' currencies. The most well-known of these is the Purchasing Power Parity (PPP) theory. PPP suggests that in the long run, exchange rates should adjust so that an identical basket of goods and services costs the same amount in any two countries when expressed in their respective currencies. This implies that the exchange rate should reflect the relative purchasing power of each currency.

For example, if a Big Mac costs $5 in the United States and €4 in Germany, the PPP exchange rate would be $5/€4 = 1.25 dollars per euro. If the actual market exchange rate is significantly different, PPP theory suggests that the currency of the country where goods are relatively cheaper will eventually appreciate against the currency of the country where goods are relatively more expensive. This appreciation would continue until the prices of goods equalize across borders, after accounting for transportation and trade barriers.

While PPP is a theoretical concept, it serves as a useful benchmark for understanding long-term currency movements. In reality, many factors can cause deviations from PPP, including differences in inflation rates, trade barriers (tariffs, quotas), transportation costs, and non-tradable goods and services. Despite these limitations, PPP is widely used by economists and international organizations to compare economic productivity and living standards across countries by converting currencies to a common standard. Other, less common, parity theories include Interest Rate Parity and Uncovered Interest Rate Parity, which focus on the relationship between interest rates and exchange rates rather than the price of goods.