In India, National Income is calculated by the combined method. It combines two methods i.e product or output method and the income method. This is done to overcome the problem of deficiency of statistics. The product method endeavours to find out the net contribution to national income of all producing units. The income method adds up income and payments accruing of factors of production. This method is used in the tertiary  sector like government services banking etc and also in the commoity sector if output data is not available.