Economics: How Leakages Limit the Fiscal Multiplier

The fiscal multiplier effect explains how an initial change in government spending or taxation can generate a larger final change in aggregate demand and real GDP. When an economy sits in a recessionary gap, with equilibrium output below the full-employment level Yf, expansionary fiscal policy shifts aggregate demand rightward, moving output and the price level higher along an upward-sloping short-run aggregate supply curve. The size of this ripple depends on the marginal propensity to consume, since each round of spending becomes someone else's income. The multiplier is k = 1 / (1 - MPC), so a higher MPC means a larger multiplier and a bigger eventual rise in AD. This matters because it determines how effective stimulus actually is: leakages such as taxation, saving, and imports shrink the real-world effect below the theoretical value, so the true increase in real GDP often falls short of the simple calculation.