Aggregate Demand

Aggregate demand (AD) is a core macroeconomic concept representing the sum of all spending on domestically produced final goods and services over a specified period. It is conventionally expressed by the identity:

AD = C + I + G + (X − M)

where C is household consumption, I is private investment (including business capital expenditure and residential investment), G is government consumption and investment, and (X − M) is net exports (exports minus imports). This is the same expenditure formulation used to calculate GDP, and in equilibrium AD equals real output.

The AD curve slopes downward against the price level because of three commonly cited effects: the real balance (Pigou) effect, where lower prices raise the real value of money holdings and boost consumption; the interest rate (Keynes) effect, where lower prices reduce money demand, lowering interest rates and stimulating investment; and the net export (Mundell–Fleming) effect, where lower domestic prices make exports more competitive.

AD shifts in response to changes in consumer confidence, fiscal policy (tax and spending decisions), monetary policy (interest rates and the money supply), exchange rates, and external demand. Keynesian economists, building on John Maynard Keynes's General Theory (1936), argue that AD is the primary short-run driver of output and employment, and that demand shortfalls can be offset by countercyclical fiscal or monetary stimulus. Classical and new classical economists place greater emphasis on supply-side determinants and view AD management as less effective over the long run.

Policy discussions of AD became prominent after the 2008 global financial crisis, when central banks deployed quantitative easing, and again during the COVID-19 pandemic, when governments used large fiscal transfers to support household spending. Excess AD relative to potential output is associated with demand-pull inflation; insufficient AD is associated with recessions and rising unemployment.