Fiscal Multiplier
What is Fiscal Multiplier?
The fiscal multiplier is the change in real output produced by a one dollar change in government spending or taxes.
The mechanism is the chain of re-spending behind the textbook multiplier: a dollar of government purchases becomes income for someone who spends part of it, and so on through the rounds. Measured multipliers come in far below the textbook value because each round leaks into saving, taxes and imports, and because a central bank may raise interest rates in response, crowding out private investment and offsetting the stimulus. Size depends on the state of the economy: with idle capacity, credit constrained households and policy rates stuck at their floor so no monetary offset arrives, multipliers are largest, while at full employment with an inflation targeting central bank they can fall to zero. Purchases of goods and services multiply more than tax cuts or transfers, because the first round of a tax cut is partly saved. Estimates vary widely across studies, since fiscal policy usually responds to the economy, which makes cause and effect hard to separate.
Fiscal Multiplier: a worked example
Start with a marginal propensity to consume of 0.8 and no other leakages: the textbook multiplier is 1 divided by 0.2, which is 5, so $50 billion of purchases would add $250 billion to GDP. Now add a marginal tax rate of 0.25 and a marginal propensity to import of 0.15. The denominator becomes 1 minus 0.8 times 0.75, plus 0.15, which is 1 minus 0.6 plus 0.15, or 0.55, so the multiplier is 1 divided by 0.55, about 1.82, and the same $50 billion adds about $90.9 billion. Suppose the extra borrowing lifts interest rates enough to cut private investment by $15 billion. That withdrawal multiplies as well, subtracting 1.82 times $15 billion, or $27.3 billion, which leaves a net gain of $63.6 billion. The multiplier an economist would measure is $63.6 billion divided by $50 billion, about 1.27, a long way from 5.
The mistake students make with fiscal multiplier
Asked for the fiscal multiplier with an MPC of 0.8, students answer 5 and present it as the real effect of a stimulus package. That figure is the ceiling of a closed model with no taxes, no imports, no monetary response and spare capacity, and dropping any one of those assumptions cuts it. Empirical estimates land much nearer 1, below it in open economies near full employment and above it when policy rates cannot fall any further. A second error applies the spending multiplier to a tax cut, when the tax multiplier is negative MPC divided by 1 minus MPC, so an MPC of 0.8 gives 5 for spending but negative 4 for taxes.
Fiscal Multiplier questions
What is a typical size for the fiscal multiplier?
Estimates cluster around 1 in normal conditions, inside a wide band running from well below 1 up to roughly 2. Values sit at the low end in small open economies with high import shares and a central bank free to raise rates, and at the high end in deep downturns with idle capacity and policy rates already at their floor. That spread is genuine rather than measurement noise, because the multiplier is a property of the situation, not a fixed constant of an economy.
Why is the spending multiplier larger than the tax multiplier?
Government purchases enter the spending stream at full strength, since every dollar of a road contract is a dollar of demand in the first round. A tax cut instead gives households a dollar of disposable income and they save part of it, so only the marginal propensity to consume times that dollar reaches demand in round one. With an MPC of 0.8 the spending multiplier is 5 and the tax multiplier is negative 4, and the ratio between them is exactly the MPC.
Can the fiscal multiplier be zero or negative?
Yes. At full employment extra government spending mainly bids resources away from private users, and a central bank targeting inflation raises rates against it, so real output barely moves and the multiplier approaches zero. It can turn negative if the fiscal expansion raises expectations of future taxes or default enough to depress private spending by more than the stimulus adds, the argument behind claims of expansionary fiscal contraction, though that result requires unusual conditions and remains contested.
Formula / Example
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