Methods of Measuring National Income

Because production, income and expenditure are equal in value (Section 2), national income can be measured by adding up any one of the three from every producing unit, income-earner, or spender in the economy.

1. Product (Value Added) Method — Add up the Gross Value Added (GVA) of every producing unit across the primary (agriculture, mining), secondary (manufacturing, construction) and tertiary (trade, banking, services) sectors.

Precautions: count only the value added at each stage, never the gross value of output (to avoid double counting); exclude the sale of second-hand goods (no new production occurs) and purely financial transactions such as buying shares (no addition to the flow of goods/services).

2. Income Method — Add up the factor incomes earned by all normal residents:

Precautions: exclude transfer incomes (old-age pensions, scholarships, gifts — these have no corresponding contribution to production) and windfall gains (lottery winnings) or the sale of second-hand assets.

3. Expenditure Method — Add up final expenditure incurred by all sectors of the economy on final goods and services:

where $C$ = private final consumption expenditure, $I$ = gross domestic capital formation (investment), $G$ = government final consumption expenditure, and $(X - M)$ = net exports (exports minus imports). …