Definition
Purchasing Power Parity (PPP) is a conversion rate used to compare the real purchasing power of different currencies. It is calculated as the ratio of amounts needed to purchase the same basket of goods and services in each country, reflecting actual cost-of-living differences.
Difference from Market Exchange Rates
Market exchange rates are determined by supply and demand in financial markets and do not reflect domestic price levels. PPP uses the criterion of how much it costs to buy the same goods, making it more suitable for international comparisons of living standards.
The Big Mac Index is a well-known simplified version of PPP. If a Big Mac costs 450 yen in Japan and 5.50 dollars in the US, the implied PPP rate is about 82 yen per dollar, which often differs from the market rate.
Role in World Rankings
MyRank's income rankings use PPP conversion factors published by the World Bank to transform each country's income into comparable terms. This prevents undervaluation of incomes in countries with lower price levels and enables rankings based on actual living standards.
Limitations
PPP calculations rely on price surveys that are conducted infrequently and involve subjective choices about which goods to include. Quality differences across countries are difficult to adjust for, and rapid inflation can make PPP estimates outdated quickly.