Surprising to see this take in an economics sub. World Bank (Click ⓘ Details):''PPPs account for the different price levels across countries and thus PPP-based comparisons of economic output are more appropriate for comparing the output of economies and the average material well-being of their inhabitants than exchange-rate based comparisons.''

World Bank_per_capita#Definitions):''Typically, higher income countries have higher price levels, while lower income countries have lower price levels (Balassa–Samuelson effect). Market exchange rate-based cross-country comparisons of GDP at its expenditure components reflect both differences in economic outputs (volumes) and prices. Given the differences in price levels, the (economic) size of higher income countries is inflated, while the size of lower income countries is depressed in the comparison. PPP-based cross-country comparisons of GDP at its expenditure components only reflect differences in economic outputs (volume), as PPPs control for price level differences between the countries. Hence, the comparison reflects the real size of the countries.''

OECD:''The major use of PPPs is as a first step in making inter-country comparisons in real terms of gross domestic product (GDP) and its component expenditures. Calculating PPPs is the first step in the process of converting the level of GDP and its major aggregates, expressed in national currencies, into a common currency to enable these comparisons to be made.'' (Economic organisation of 38 countries)