Net national income

Net national income (NNI) is a type of national income accounting defined as gross national income minus the depreciation of fixed capital assets (dwellings, buildings, machinery, transport equipment and physical infrastructure) through wear and tear and obsolescence. In that sense it is very similar to Net Domestic Product.

Formula
The formula for calculating net national income is: NNI = C + I + G + NX + NFF - IT - D

Where C is consumption, I is investment, G is government spending, NX refers to imports minus exports, NFF is net foreign factors, IT are any indirect taxes, and D is capital depreciation. A somewhat obscure variant of NIA it often takes a back seat to more prominent indicators like GDP and GDI.