Different countries have dramatically different levels of economic development. One income per head of population, or the total annual income received by a resident of a nation. Japan, sweden, switzerland, and us are among the richest on that measure, while. China and india are the poorest. common measure for the economic development is a country"s gni: gross national. However, gni measure don"t consider differences in cost of living. To account those differences, one can adjust gni per capita by purchasing power: the purchasing power parity (ppp). The base of adjustment is usa, others are ranked on whether the cost of living is higher or lower than in the usa. Now, the differences in gni/ppp can mislead too: Does not show differences within population: indian people 7% of what an. American can afford, however 250 millions is a fairly wealthy middle class. Some countries have important unofficial markets (black market): accounts for.