The expenditure approach decomposes GDP into four categories: Consumption (C) — household spending on goods and services; Investment (I) — business spending on capital and housing, plus inventory changes; Government purchases (G) — federal, state, and local spending on goods and services (excludes transfer payments); and Net Exports (NX = exports minus imports). Understanding each component's size and cyclical behavior is essential for analyzing policy and forecasting.
Look up the actual shares of C, I, G, and NX in US GDP and compare to a developing economy. Classify borderline cases: Is a haircut consumption? Is buying a stock investment? (Answer: it depends on who's asking.)
From your study of GDP and national income, you know that GDP measures the total market value of final goods and services produced within a country in a given period. The expenditure approach — GDP = C + I + G + NX — breaks that total down by *who does the buying*. Each component captures a distinct sector of the economy and has its own cyclical behavior, making the decomposition essential for understanding recessions, policy responses, and international trade.
Consumption (C) is the largest component in most advanced economies, typically around 65–70% of US GDP. It includes all household spending on goods (durable goods like cars, nondurable goods like food) and services (healthcare, education, haircuts). Because it is so large, even modest shifts in consumer confidence or spending have major macroeconomic effects. Consumption tends to be relatively stable across the business cycle — households smooth their spending — but it is sensitive to interest rates, wealth effects (especially housing prices), and income.
Investment (I) is smaller but much more volatile, making it the primary driver of business-cycle fluctuations. In GDP accounting, Investment means business fixed investment (machinery, equipment, structures), residential investment (new housing construction), and changes in business inventories. It does NOT include financial investment — buying stocks or bonds is a transfer of ownership of existing assets, not the creation of new capital. This definitional distinction trips up many students. Investment is highly sensitive to interest rates and business expectations, which is why it collapses sharply in recessions.
Government purchases (G) cover federal, state, and local spending on goods and services — everything from military equipment to teacher salaries to road construction. What is excluded is critical: transfer payments like Social Security, Medicaid, and unemployment insurance are not in G. Why? Because no new good or service is produced when the government sends a check; the recipient's subsequent spending shows up in C. Including transfers in G would count the same real output twice. This exclusion surprises many students who associate government spending broadly with G.
Net Exports (NX = Exports − Imports) is the only component that can be negative, and in the US it typically is (a trade deficit). Exports add to GDP because foreigners are buying domestically produced goods. Imports are subtracted not as a penalty but as a correction: C, I, and G measure total domestic spending, which includes spending on imports. Since imports represent foreign production, subtracting them ensures only domestically produced output enters GDP. A domestic consumer buying a German car really does spend money — it appears in C — but that spending also exits as an import subtraction in NX, leaving zero net contribution to GDP. The accounting identity holds regardless of the trade balance.