Expenditure Method

The Expenditure Method: Measuring GDP from the Demand Side

The expenditure method offers a second, independent way to calculate GDP. Instead of adding up the value added at each stage of production (the value-added method), this approach looks at the total spending on final goods and services produced within the domestic economy. The core idea is simple: every rupee of output produced must eventually be bought by someone. By adding up all such purchases, we arrive at the same GDP figure.

The Logic: Revisiting the Farmer-Baker Economy

To see how this works, return to the simple two-firm economy of the farmer and the baker. The farmer produces wheat worth ₹100. The baker buys ₹50 worth of wheat as an intermediate good and uses it to produce bread worth ₹200.

In the expenditure method, we add only final expenditures — spending on goods that are not used up as intermediate inputs in further production. The baker's purchase of wheat (₹50) is an intermediate expenditure and is therefore excluded. The final expenditures in this economy are:

• The baker sells bread worth ₹200 to households. This is final consumption expenditure.
• The farmer sells wheat worth ₹50 directly to households (for their own consumption). This is also final consumption expenditure.

The aggregate value of output by the expenditure method is ₹200 (from the baker) + ₹50 (from the farmer) = ₹250 per year — exactly the same result as the value-added method.

Breaking Down a Firm's Final Revenue

For any individual firm i, its total revenue from final sales comes from four distinct sources. These are the four components of aggregate demand that the firm faces.

1. Final Consumption Expenditure ($C_i$): Spending by households on the goods and services produced by firm i. While households are the primary source, firms may also make consumption expenditures (e.g., buying tea or snacks for employees or guests).
2. Final Investment Expenditure ($I_i$): Spending by other firms on capital goods produced by firm i. This includes machinery, factory buildings, and equipment. A critical distinction: expenditure on intermediate goods is excluded from GDP, but expenditure on investment goods is included. Why? Because investment goods are not consumed in the production process; they remain with the firm and contribute to future production.
3. Government Final Expenditure ($G_i$): Spending by the government on the final goods and services produced by firm i. This includes both government consumption (e.g., stationery for an office) and government investment (e.g., building a road).
4. Export Revenue ($X_i$): Revenue firm i earns from selling its goods and services to buyers abroad.

The total revenue of firm i from final sales is therefore:

Aggregating Across All Firms

If there are $N$ firms in the economy, the sum of all their final revenues is:

This sum, $\sum RV_i$, is precisely the GDP according to the expenditure method. But we need to express it in terms of economy-wide aggregates.

From Firm Revenues to National Aggregates

Let’s define the economy-wide aggregates:

• $C$ = Aggregate final consumption expenditure of the entire economy.
• $I$ = Aggregate final investment expenditure of the entire economy.
• $G$ = Aggregate final government expenditure of the entire economy.
• $X$ = Aggregate export revenue of the entire economy ($X \equiv \sum_{i=1}^{N} X_i$).

However, a portion of this spending goes to foreign producers — it is spent on imports. We must subtract imports to isolate the spending that reaches domestic firms.

• $C_m$ = Expenditure on imports of consumption goods. Therefore, spending on domestic consumption goods is $C - C_m$.
• $I_m$ = Expenditure on imports of investment goods. Therefore, spending on domestic investment goods is $I - I_m$.
• $G_m$ = Expenditure on imports of government goods. Therefore, spending on domestic government goods is $G - G_m$.

Now we can rewrite the sums from Equation (2.3) in terms of these aggregates:

• $\sum_{i=1}^{N} C_i \equiv C - C_m$
• $\sum_{i=1}^{N} I_i \equiv I - I_m$
• $\sum_{i=1}^{N} G_i \equiv G - G_m$

Substituting these into Equation (2.3):

Rearranging:

Let $M \equiv C_m + I_m + G_m$ be the economy's total import expenditure. Then:

Since $\sum RV_i$ is GDP, we arrive at the fundamental expenditure identity.