There are 3 methods of measuring national income: 1) Value added method or product method which measures domestic income by estimating the contribution of each producing enterprise in the domestic territory. 2) Income method 3) Expenditure method The value added method involves classifying production units, estimating the gross value added of each unit as the difference between output value and intermediate consumption, and measuring output value as sales plus change in stock. National income is then calculated by adjusting GDP for net factor income from abroad, depreciation, and net indirect taxes.