The main criterion used by the World Bank in classifying different countries is per capita income. Per capita income :- When total income of a country is divided by the total population, then per capita income is arrived at. Those countries whose per capita income is more than Rs. 4,53000 per year are called rich countries and those whose income is less than Rs. 37000 are called poor countries. Limitations:- Although this method is used widely it does not give accurate picture of development. For example, in calculating income, every one is supposed to have that amount but actually large number of poor people donot have that amount.