Long-Run Adjustment to Macroeconomic Shocks — AP Macroeconomics
1. Core Concepts of Long-Run Adjustment ★★☆☆☆ ⏱ 3 min
Long-run adjustment to macroeconomic shocks describes how an economy returns to potential output ($Y_p$) after a short-run shock pushes output away from long-run equilibrium. This topic makes up 10-15% of AP Macroeconomics Unit 3, corresponding to 1-3% of your total exam score, tested in both multiple-choice and free-response questions.
Standard notation used in this topic: $Y_p$ = potential (full-employment) output, LRAS = long-run aggregate supply (vertical at $Y_p$), SRAS = short-run aggregate supply (upward-sloping due to sticky nominal wages), AD = aggregate demand. A recessionary gap occurs when $Y < Y_p$, and an inflationary gap occurs when $Y > Y_p$.
2. Adjustment to Demand-Side Shocks ★★☆☆☆ ⏱ 4 min
Demand-side shocks are unexpected shifts of aggregate demand caused by changes in consumer spending, investment, government spending, or net exports. After any demand shock, the economy diverges from potential output in the short run due to sticky nominal wages, which do not adjust immediately to price changes. In the long run, wages adjust to reflect new price levels, shifting SRAS to return output to potential GDP.
- **Positive demand shock (AD shifts right):** Short-run equilibrium has $Y > Y_p$ (inflationary gap) with higher prices. Higher prices reduce real wages, so workers negotiate higher nominal wages, increasing firm production costs, shifting SRAS left. Final outcome: $Y=Y_p$ at a permanently higher price level.
- **Negative demand shock (AD shifts left):** Short-run equilibrium has $Y < Y_p$ (recessionary gap) with lower prices. Higher cyclical unemployment leads workers to accept lower nominal wages, reducing firm production costs, shifting SRAS right. Final outcome: $Y=Y_p$ at a permanently lower price level.
Exam tip: On FRQs, always explicitly label which curve shifts and why; AP graders award separate points for correctly identifying the SRAS shift and its cause during self-correction.
3. Adjustment to Supply-Side Shocks ★★★☆☆ ⏱ 4 min
Supply-side shocks are unexpected shifts of short-run aggregate supply caused by changes in input prices, natural disasters, or productivity changes. Temporary supply-side shocks only shift SRAS, while permanent supply-side shocks shift both SRAS and LRAS because they change potential output. The most common exam question involves negative temporary supply shocks, which cause stagflation: a combination of stagnant output (high unemployment) and higher inflation.
For a temporary negative supply shock (SRAS shifts left): Short-run equilibrium is at $Y < Y_p$ and a higher price level. Without policy intervention, high unemployment leads to lower nominal wages over time, reducing production costs, so SRAS shifts back right to its original position, returning output to the original $Y_p$ and original price level. For a permanent negative supply shock (e.g., permanent oil price increase): SRAS shifts left and LRAS also shifts left to the new lower $Y_p$, so the final equilibrium stays at the new lower output and permanently higher price.
Exam tip: If the question does not specify the shock is permanent, assume it is temporary; only shift LRAS if the question explicitly states that potential output has changed.
4. Policy Intervention vs. Self-Correction ★★★☆☆ ⏱ 3 min
When the economy is in an output gap, policymakers can choose to use fiscal or monetary policy to shift AD and close the gap, instead of waiting for slow self-correction via SRAS shifts. This tradeoff between faster adjustment and price level changes is a core concept tested on the AP exam.
For a recessionary gap: Self-correction takes several years of high unemployment. Expansionary policy shifts AD right, closing the gap much faster, but results in a permanently higher price level than self-correction. For an inflationary gap: Contractionary policy shifts AD left, closing the gap faster and preventing sustained inflation, but results in a lower price level than self-correction. For stagflation from a negative supply shock, policymakers face a painful tradeoff: expansionary policy to close the recessionary gap leads to permanently higher inflation, while contractionary policy to reduce inflation deepens the recession.
Exam tip: Always remember: self-correction shifts SRAS, policy intervention shifts AD. Mixing up which curve shifts is one of the most common sources of point loss on the exam.
Common Pitfalls
Why: Students confuse policy intervention with the self-correcting mechanism, and default to shifting AD for any adjustment.
Why: Students confuse short-run equilibrium with long-run equilibrium, forgetting LRAS is vertical at potential output, so final long-run equilibrium must intersect LRAS by definition.
Why: Students confuse shifts of SRAS with shifts of LRAS, thinking any change in equilibrium shifts the long-run aggregate supply curve.
Why: Students forget that the temporary SRAS shift reverses in self-correction.
Why: Students confuse short-run output gains with long-run potential output, forgetting that wages adjust to erase the output gap.
Why: Students confuse short-run output effects with long-run outcomes.