The income of all the residents of the country is called the income of the country. States and countries cannot be compared by the total income of the country because different countries and states have different sizes of the population. Therefore, Countries or states are always compared by using the Average Income of both.Average income is calculated by := Total income / Total populationThis criterion is also used as per World Development Reports by the World Bank for classifying countries into various categories like rich countries or low-level income countries etc.