Aggregate DEMAND (AD) or domestic final demand (DFD) is the total demand for final goods and services in an economy at a given time.[1] It specifies the amounts of goods and services that will be purchased at all possible price levels.[2] This is the demand for the gross domestic product of a country. It is often called effective demand, though at other times this term is distinguished.

The aggregate demand curve is plotted with real output on the horizontal AXIS and the price level on the VERTICAL axis. It is downward sloping as a result of three distinct effects: Pigou's wealth effect, KEYNES' interest rate effect and the Mundell–Fleming exchange-rate effect. The Pigou effect states that a higher price level implies lower real wealth and therefore lower consumption spending, giving a lower quantity of goods demanded in the aggregate. The Keynes effect states that a higher price level implies a lower real money supply and therefore higher interest rates resulting from financial market equilibrium, in turn resulting in lower investment spending on new physical CAPITAL and hence a lower quantity of goods being demanded in the aggregate.