Chapter 13 · Demand-side and supply-side policies
Expansionary demand-management policy
Use AD–AS to explain how expansionary fiscal or monetary policy can close a recessionary gap. Compare output gains and inflationary pressure.
The economic idea
Macroeconomic policy uses demand-side and supply-side measures to pursue objectives such as stable prices, low unemployment, sustainable growth and a stable external position. Demand-side policy changes aggregate demand; supply-side policy changes productive capacity, efficiency or the natural rate of unemployment.
Fiscal policy is the use of government expenditure and taxation to influence aggregate demand, resource allocation and income distribution. Discretionary fiscal policy is a deliberate change, while automatic stabilizers such as progressive taxation and unemployment benefits respond without a new policy decision.
Monetary policy is action by a central bank to influence financial conditions and aggregate demand. Conventional policy changes a policy interest rate; other measures include asset purchases, credit facilities, reserve tools and communication about future policy.
Expansionary policy raises aggregate demand through higher government expenditure, lower taxation, lower interest rates or easier credit. Contractionary policy lowers aggregate demand through the opposite changes. The appropriate stance depends on the output gap and the source of inflation or unemployment.
Demand management cannot directly remove structural unemployment or permanently increase productive capacity. Supply-side policies may complement it, but usually operate through different channels and longer time horizons.
Reading the current policy movement from AD₁ to AD₂
“Price level” is measured vertically and “Real GDP” horizontally.
“AD₁” records initial planned expenditure and “AD₂” the current post-policy level. “SRAS” is held fixed.
“LRAS” marks potential output. “E₁” and “E₂” identify the initial and post-policy macroeconomic equilibria.
Initial condition: E₁
“AD₁” intersects “SRAS” at “E₁”, establishing “Y₁” and “PL₁”. Relative to “LRAS”, the economy initially shows a recessionary gap.
Policy movement: AD₁ to AD₂
“AD₂” lies to the right of “AD₁”. Real GDP rises from “Y₁” to “Y₂”, while the price level rises from “PL₁” to “PL₂”. “E₂” lies at “LRAS”, so the output gap is closed in the current state.
Post-policy equilibrium: E₂
“AD₂” intersects the unchanged “SRAS” at “E₂”, establishing “Y₂” and “PL₂”. “E₂” lies at “LRAS”, so the output gap is closed in the current state.
Show how the policy reaches aggregate demand
Higher government purchases enter AD directly through G. A cut in income tax instead raises disposable income; AD rises to the extent that households spend the additional income. A lower interest rate may encourage consumption and investment by reducing borrowing costs.
Choose the chain that fits the policy in the question. Then explain the output and price-level response. Confidence, leakages, spare capacity and time lags affect the result, so an AD arrow is not a complete policy explanation.
From a policy decision to the current AD–AS outcome
A fiscal authority increases expenditure or reduces taxes, or a central bank eases financial conditions.
Consumption, investment, government spending or net exports increase, shifting aggregate demand from “AD₁” toward “AD₂”.
Firms respond to the change in planned expenditure by moving along “SRAS”, altering output, employment and the price level.
Common mistakes to avoid
- “AD₂” is not automatically expansionary or contractionary because of the page title; its position relative to “AD₁” determines the direction shown.
- Closing a gap means moving equilibrium output toward “LRAS”, not merely shifting “AD₁” by a large distance.
- Fiscal and monetary policy can produce a similar AD shift but use different instruments, institutions and transmission channels.
- A reduction in the price level in a comparative-equilibrium diagram is not automatically a sustained fall in the inflation rate over time.
- The model does not show the budget balance, public debt, policy interest rate, exchange rate or distributional effects.
How to draw this diagram
- Title the diagram “Expansionary demand-management policy”. Label the horizontal axis “Real GDP” and the vertical axis “Price level”.
- Draw AD₁ first and label it clearly.
- Draw SRAS next and label it clearly.
- Draw AD₂ next and label it clearly.
- Draw LRAS next and label it clearly.
- Mark each relevant intersection and distinguish the initial, market and socially optimum or policy outcomes where applicable.
- Project important intersections to the axes with dashed guide lines and label the outcomes.
- Check that every symbol used in the explanation appears on the diagram and add arrows showing the direction of change.
Assumptions and limitations
- The diagram combines many possible fiscal and monetary instruments into one aggregate-demand shift and cannot identify which instrument was used.
- It compares equilibria rather than showing recognition, decision, implementation and impact lags.
- Potential output and SRAS are held fixed even though investment, hysteresis, commodity prices and expectations can change them.
- Multiplier, exchange-rate, financial-stability, public-debt and distributional effects are not plotted.
- The model does not determine the optimal policy mix or prove that the estimated output gap is correct.