Fiscal Multiplier
The fiscal multiplier is the ratio of the change in output to the change in government spending or taxation that causes it. It measures the effectiveness of fiscal policy: a multiplier greater than one means that a given change in the fiscal stance produces a larger change in output, while a multiplier less than one means that part of the stimulus leaks away. The size of the multiplier is central to debates about the design of stimulus and consolidation, and it depends on the state of the economy, on the policy response of the central bank, and on the structure of the measures.
Derivation
The multiplier arises because an initial change in spending raises incomes, part of which is spent, generating further income and further spending. In the simplest Keynesian model, with a closed economy and no taxation, the multiplier equals one divided by one minus the marginal propensity to consume. If the marginal propensity to consume is eight-tenths, the multiplier is five, so an increase in spending of one unit raises output by five units.
Extensions modify the result. Taxation reduces the multiplier, because part of any increase in income accrues to the government rather than being spent. Imports also reduce it, because part of the spending leaks abroad. In an open economy with taxes, the multiplier is smaller than in the simple closed-economy case. The composition of the fiscal change matters too: spending on goods and services typically has a larger multiplier than a tax cut of the same size, because spending directly adds to demand while a tax cut is partly saved.
Determinants of the size
The size of the multiplier depends on several conditions. When the economy has spare capacity, additional demand raises output rather than prices, and the multiplier is larger. When the economy is near full employment, additional demand is absorbed by higher prices, and the multiplier is smaller. The state of the labour market, the extent of rigidities, and the openness of the economy all influence the outcome.
The response of monetary policy is critical. If the central bank keeps interest rates unchanged, as happens when rates are already at their lower bound, the fiscal expansion is not offset and the multiplier is large. If the central bank raises rates to keep inflation under control, the expansion is partly crowded out and the multiplier is small. The interaction between fiscal and monetary policy therefore determines the effectiveness of fiscal measures, and coordination between the two can raise the multiplier.
Empirical evidence
Empirical estimates of the multiplier vary widely. Estimates from macroeconomic models are typically in the range of one half to one and a half in normal times, with larger values when policy rates are constrained. Evidence from historical episodes, including wars and large fiscal programmes, and from cross-country comparisons, suggests that multipliers can be larger during deep recessions and when monetary policy is accommodative.
Modern research uses identified fiscal shocks, such as changes in spending driven by political or military events, to estimate causal effects. These studies tend to find larger multipliers during downturns and smaller ones during expansions, supporting the view that the multiplier is state-dependent. There is, however, considerable uncertainty, and estimates vary with the method, the sample, and the definition of the fiscal change.
Policy implications
The multiplier is central to the case for discretionary fiscal action. If the multiplier is large, a given increase in spending produces a large increase in output, and the case for using fiscal policy to combat recessions is strong. If the multiplier is small, the benefits are limited and the debt incurred may not be justified. The state-dependence of the multiplier implies that fiscal policy is most effective precisely when it is most needed, in deep downturns.
The multiplier also matters for consolidation. When governments reduce spending or raise taxes to lower debt, the contractionary effect depends on the multiplier: a large multiplier means a larger fall in output for a given fiscal adjustment. Understanding the multiplier helps policymakers to sequence and design measures, to protect the most vulnerable, and to calibrate support, and it informs the design of fiscal frameworks that allow flexibility in bad times while ensuring sustainability over the cycle.
Open economy and regional multipliers
In an open economy, part of any fiscal expansion leaks into imports, reducing the domestic multiplier. The size of the leakage depends on the marginal propensity to import, which is higher for small, open economies. For this reason, the multiplier is generally smaller in countries that trade intensively, and fiscal expansion in one country may raise demand in its trading partners, an effect known as a fiscal spillover that can be a source of international interdependence.
Within a country, the multiplier varies across regions. A fiscal expansion in a region with spare capacity and low import leakage produces a larger local effect than one in a region where capacity is tight or where spending quickly leaks elsewhere. Regional multipliers matter for the design of place-based policies and for the assessment of the local effects of national measures, and they help to explain why the same policy can have different effects in different areas.
State dependence and nonlinearity
The dependence of the multiplier on the state of the economy is one of the most robust findings in the literature. During deep recessions, when unemployment is high and policy rates are near their lower bound, the multiplier tends to be larger, sometimes substantially above one. During expansions, when resources are fully employed, it tends to be smaller, and fiscal expansion may simply crowd out private activity.
This nonlinearity has important implications. It implies that fiscal policy is most effective when it is most needed, and that the cost of fiscal expansion, in terms of debt incurred, is lowest when the expansion produces the largest increase in output. It also implies that the appropriate fiscal stance depends on conditions, and that rules which ignore the state of the economy may be ill-suited to stabilisation. Recognising state dependence supports the case for countercyclical policy.
Measurement challenges
Estimating the multiplier is difficult because fiscal policy responds to the economy as well as affecting it. Governments spend more and tax less when the economy weakens, so a simple correlation between deficits and output conflates the effect of policy with the effect of the cycle. Identifying the causal effect requires isolating the part of fiscal change that is independent of current conditions, using instruments, narrative records, or timing rules.
Different methods yield different estimates, and the range of published results is wide. The choice of method, the sample, and the definition of the fiscal shock all influence the estimate. Analysts therefore report ranges and emphasise the uncertainty, and they use several approaches to check robustness. The practical implication is that the multiplier should be treated as an estimate with a range, and that policy design should be robust to the possibility that the true value differs from the central estimate.