Q.Write down the three identities of calculating the GDP of a country by the three methods. Also briefly explain why each of these should give us the same value of GDP.

The three methods of calculating GDP correspond to the three sides of the circular flow of income: production, expenditure, and income. Each method measures the same economic activity from a different vantage point, so they must yield the same total.

1. Product Method (Value Added Method)

GDP = Sum of gross value added (GVA) by all producing units in the domestic territory over a year.

GVA = Value of output – Value of intermediate consumption.

This method avoids double-counting by only counting the value added at each stage of production.

2. Expenditure Method

GDP = $C + I + G + (X - M)$

where:

$C$ = private final consumption expenditure

$I$ = gross domestic capital formation (investment)

$G$ = government final consumption expenditure

$X$ = exports, $M$ = imports

This method sums up all final uses of goods and services produced domestically.

3. Income Method

GDP = Compensation of employees + Operating surplus (rent, interest, profit) + Mixed income of self-employed + Net indirect taxes (indirect taxes – subsidies) + Depreciation

This method adds up all factor incomes generated in the production process. …

The Three Identities of GDP Calculation

National income accounting rests on a simple but powerful idea: in any economy, what is produced must be bought, and what is bought generates income for someone. This circular flow gives us three distinct but equivalent ways to measure GDP.

1. Product Method (Value Added Method)

This method sums the value added at each stage of production across all firms in the economy. Value added is the difference between the value of a firm's output and the value of intermediate goods it purchases from other firms.

The logic is straightforward: by adding only the fresh value created at each step, we avoid double-counting the same output multiple times. For example, when a baker buys flour from a miller, the flour's value is counted only once—as part of the miller's value added—and not again when the baker sells the bread.

2. Expenditure Method

This method measures GDP as the total final expenditure on goods and services produced within the domestic territory. It captures who buys the final output.

Where:

• $C$ = Private final consumption expenditure
• $I$ = Gross domestic capital formation (investment)
• $G$ = Government final consumption expenditure
• $X$ = Exports
• $M$ = Imports

The identity works because every unit of final output must be purchased by someone—households, firms, government, or foreigners (net of what we buy from abroad). If a car is produced but not sold, it shows up as inventory investment under $I$.

3. Income Method

This method sums all factor incomes generated in the production process—the payments made to the owners of factors of production.

The components are:

• Compensation of employees: wages, salaries, and employer contributions to social security
• Operating surplus: profits, rent, and interest earned by firms
• Mixed income: income of self-employed persons (where labour and capital inputs cannot be separated)
• Depreciation: consumption of fixed capital
• Net indirect taxes: indirect taxes minus subsidies

Why All Three Give the Same Value

The equivalence is not a coincidence—it is an accounting identity built into the circular flow of the economy. …