GDP deflator
Where PPPrateX,i is the PPP exchange rate of country X for year i, PPPrateX,b is the PPP exchange rate of country X for the benchmark year, PPPrateU,b is the PPP exchange rate of the United States (US) for the benchmark year (equal to 1), GDPdefX,i is the GDP deflator of country X for year i, GDPdefX,b is the GDP deflator of country X for the benchmark year, GDPdefU,i is the GDP deflator of the US for year i, and GDPdefU,b is the GDP deflator of the US for the benchmark year.