I did not say it is not used totally but for the purpose of country to country comparison, GDP norminal is better preferred. Ngoja nikupostie link from Wikipedia ya GDP hizo mbili ndio ufahamu tofauti. By the way World bank huwa inatumia GDP norminal kucalculate GNI. As I have said, kama GDP PPP ingekuwa soooo important then China ingekuwa the biggest economy in the world na Tanzania ingekuwa bigger than Kenya. But unfortunately for you, GDP PPP is usually used only as an indicator of purchasing power of one country relative to another. Yaani mzungu akiwa na $100 anaeza purchase more goods in T.Z than in Kenya. Or to put it differently goods in T.Z are cheaper than in Kenya