The World Bank has used the Atlas method[1] since 1993 to estimate the economic size of countries based on their gross national income (GNI) in U.S. dollars.
To convert a country's GNI from its local currency to U.S. dollars, the Atlas method uses a conversion factor that averages exchange rates over three years.
[1] The World Bank prefers the Atlas method for comparing the economic sizes of countries.
It is used to categorize countries into low, middle, and high-income groups and to determine their eligibility for loans.
This method helps avoid abrupt changes in country classification due to short-term economic fluctuations.