AS & A-Level Economics — Policy Evaluation and External Adjustment

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Original Deckloop economics study material on policy evaluation and external adjustment, with 100 practice cards and 20 concept explainers. Includes worked applications and analytical reasoning.

Economics EN A-Level

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Fiscal Multipliers, Crowding Out, and Capacity

A fiscal multiplier is the change in national income per unit of a specified fiscal change. Government purchases add directly to spending; tax changes initially affect disposable income and therefore consumption. Successive rounds of spending can amplify the initial demand change. In a simple fixed-price model, the government-spending multiplier is k = 1 / (MPS + MPT + MPM), with saving, tax and import leakages all measured per extra unit of total income. Tax multipliers differ because the initial consumption response is indirect. Real-world effects also depend on spare capacity, financing and monetary policy. Government borrowing may raise interest rates and reduce private expenditure, while demand near productive capacity can displace other resource uses. These forms of crowding out can weaken the stimulus. Spare capacity makes an output response more feasible but does not guarantee a particular multiplier or eliminate financing constraints.

Key points

A fiscal multiplier is a ratio: the national-income change divided by the specified fiscal change.
Its size is inversely related to the marginal propensity to save, tax, and import, as these are leakages from the circular flow.
Crowding out occurs when increased government borrowing raises interest rates, reducing private sector investment and consumption.
The effectiveness of fiscal policy, including the multiplier's size and the risk of crowding out, depends significantly on the economy's level of spare capacity.

Worked example

Question

A government raises infrastructure spending by 200 million monetary units. Assume a fixed-price model with spare capacity, unchanged interest rates, and marginal leakages from total income of 0.15 into saving, 0.05 into taxes and 0.10 into imports. Calculate the government-spending multiplier and predicted income change, retaining full precision until the final answer.

Solution

1. Add the marginal leakages: 0.15 + 0.05 + 0.10 = 0.30.
2. The multiplier is 1 / 0.30 = 3.333… .
3. Calculate the income change without rounding the multiplier: 200 million / 0.30 = 666.666… million.
4. Round only the final results: k ≈ 3.33 and the income change ≈ 666.67 million monetary units.

Under the stated model assumptions, the multiplier is approximately 3.33 and national income rises by approximately 666.67 million monetary units.

Common pitfalls

Misconception: Believing the fiscal multiplier only applies to government spending, not tax changes. Correction: The multiplier effect also applies to changes in taxation, though the initial impact on aggregate demand is indirect (via disposable income) and typically smaller for an equivalent monetary value compared to direct government spending.
Misconception: Crowding out always cancels the entire stimulus. Correction: Its extent depends on capacity, financing, interest-rate responses and monetary policy. It can be partial, substantial or absent under different assumptions; do not assume a universal size.

Prerequisites

Deck 07 — Deficit Flow Versus Debt Stock: To understand the distinction between a budget deficit (flow) and national debt (stock), which is fundamental to understanding government borrowing and the financing aspect of crowding out.
Deck 07 — Fiscal Policy in the AD-AS Model: To understand how fiscal policy (changes in government spending or taxation) influences aggregate demand and national income within the AD-AS framework.
Deck 14 — The Multiplier as Repeated Expenditure Rounds: To understand the core mechanism of the multiplier effect, where an initial injection leads to successive rounds of expenditure and income generation.
Deck 14 — Actual Output, Potential Output and Output Gaps: To understand the concept of actual and potential output, which is essential for grasping how spare capacity influences the effectiveness of fiscal policy and the risk of crowding out.