Core Concepts & Learning Goals
This topic explores the economy's powerful, built-in ability to "heal itself." While economic shocks can push output and employment away from their ideal levels in the short run, the economy has a natural tendency to return to its long-run potential over time. This process is known as long-run self-adjustment.
The core idea is that wages and other resource prices, which can be "sticky" or slow to change in the short run, are flexible in the long run. This flexibility is the key mechanism that guides the economy back to full employment. By the end of this section, you will be able to explain, using the aggregate demand-aggregate supply model, how output, employment, and the price level respond to economic shocks and return to their long-run equilibrium without any government intervention.
Key Concepts Breakdown
1. The Foundation: Flexible Wages and Prices
The entire theory of long-run self-adjustment rests on one critical assumption: wages and input prices are flexible in the long run.
Sticky Wages: In the short run, nominal wages are often slow to change due to contracts, social norms, or minimum wage laws. This is why a drop in aggregate demand can cause unemployment rather than an immediate drop in wages.
Flexible Wages: In the long run, these barriers fade. Labor contracts expire and can be renegotiated. Workers' expectations about inflation adjust. Therefore, a period of high unemployment will eventually lead to falling nominal wages, and a period of labor shortages will lead to rising nominal wages. This flexibility in input costs is what drives the economy's return to full employment.
2. Closing a Recessionary Gap
A recessionary gap occurs when the economy's short-run equilibrium output is below its full-employment level. This means real GDP is low and unemployment is higher than its natural rate.
The Shock: A negative shock to aggregate demand (AD), such as a decline in consumer confidence or investment, shifts the AD curve to the left.
Short-Run Effect: The economy moves to a new short-run equilibrium with a lower price level, lower real GDP, and higher unemployment.
The Long-Run Adjustment:
The high unemployment rate puts downward pressure on nominal wages. With many people looking for work, firms can hire new workers for less, and existing workers have little bargaining power to demand raises.
As nominal wages fall, the cost of production for firms decreases.
This decrease in input costs shifts the short-run aggregate supply (SRAS) curve to the right.
This rightward shift continues until the economy reaches a new long-run equilibrium back at the full-employment level of output.
Final Result: The economy returns to its potential output ((Y_F)) and the natural rate of unemployment. The only lasting change is a permanently lower price level.
3. Closing an Inflationary Gap
An inflationary gap occurs when the economy's short-run equilibrium output is above its full-employment level. The economy is "overheating," with real GDP temporarily high and unemployment below its natural rate.
The Shock: A positive shock to aggregate demand, such as an increase in government spending or a boom in exports, shifts the AD curve to the right.
Short-Run Effect: The economy moves to a new short-run equilibrium with a higher price level, higher real GDP, and lower unemployment.
The Long-Run Adjustment:
The very low unemployment rate creates a labor shortage, forcing firms to compete for workers. This competition puts upward pressure on nominal wages.
As nominal wages rise, the cost of production for firms increases.
This increase in input costs shifts the short-run aggregate supply (SRAS) curve to the left.
This leftward shift continues until the economy reaches a new long-run equilibrium back at the full-employment level of output.
Final Result: The economy returns to its potential output ((Y_F)) and the natural rate of unemployment. The only lasting change is a permanently higher price level.
4. Long-Run Aggregate Supply and Economic Growth
The self-adjustment process always brings the economy back to its current potential, represented by the vertical long-run aggregate supply (LRAS) curve. The LRAS curve is vertical at the full-employment level of output, which is the level of real GDP an economy can produce when unemployment is at its natural rate.
It is crucial to distinguish between self-adjustment and economic growth.
Self-Adjustment: The SRAS curve shifts to bring the economy back to the existing LRAS curve.
Economic Growth: The LRAS curve itself shifts to the right, indicating a permanent increase in the economy's productive capacity (e.g., due to new technology or a larger workforce). This represents a change in the full-employment level of output itself.
Graphical Analysis (Text-Only)
This analysis uses the AD-AS model to illustrate long-run self-adjustment.
Model Setup:
Vertical Axis: Price Level (PL)
Horizontal Axis: Real GDP (Y)
Curves in Initial Long-Run Equilibrium (E1):
AD1: A downward-sloping aggregate demand curve.
SRAS1: An upward-sloping short-run aggregate supply curve.
LRAS: A vertical line at the full-employment output, (Y_F).
Equilibrium Point E1: All three curves intersect at price level (PL_1) and output (Y_F).
Scenario: Adjusting from a Recessionary Gap
The Shock: Aggregate demand falls, shifting the AD curve left from AD1 to AD2.
Short-Run Equilibrium (E2):
The new short-run equilibrium is where AD2 intersects SRAS1.
At point E2, output has fallen to (Y_2) (where (Y_2 < Y_F)) and the price level has fallen to (PL_2) (where (PL_2 < PL_1)).
The economy is in a recessionary gap.
Long-Run Adjustment:
High unemployment at (Y_2) causes nominal wages to fall.
Lower wages reduce production costs, shifting the SRAS curve to the right, from SRAS1 to SRAS2.
New Long-Run Equilibrium (E3):
The new long-run equilibrium is where AD2 intersects SRAS2, which occurs on the LRAS curve.
At point E3, output has returned to (Y_F).
The price level has fallen further to (PL_3) (where (PL_3 < PL_2)).
| Stage | Price Level | Real GDP | Unemployment Rate |
|---|---|---|---|
| Initial (E1) | (PL_1) | (Y_F) | Natural Rate |
| Short-Run (E2) | (PL_2) ↓ | (Y_2) ↓ | Above Natural Rate |
| New Long-Run (E3) | (PL_3) ↓ | (Y_F) | Natural Rate |
Step-by-Step Example
Let's trace the effects of a negative shock to aggregate demand, assuming no government intervention.
Scenario: A major housing bubble bursts, causing household wealth to plummet. As a result, consumer spending falls sharply across the economy.
Step 1: The Initial Shock. The fall in consumer spending causes the aggregate demand (AD) curve to shift to the left. The economy, initially at long-run equilibrium (E1), is now out of balance.
Step 2: The Short-Run Impact. The leftward shift in AD creates a new short-run equilibrium (E2) where the new AD curve intersects the original SRAS curve. At this point, real GDP is lower than the full-employment level, and the unemployment rate is high. The price level has also decreased. The economy is now in a recessionary gap.
Step 3: The Long-Run Self-Adjustment. The high unemployment puts significant downward pressure on wages. As labor contracts come up for renewal, firms can negotiate lower nominal wages. These lower labor costs reduce firms' overall cost of production. This causes the short-run aggregate supply (SRAS) curve to begin shifting to the right.
Step 4: The New Long-Run Equilibrium. The SRAS curve continues to shift to the right until it intersects the new AD curve at the long-run aggregate supply (LRAS) curve. This is the new long-run equilibrium (E3). At this point, the economy is back at its full-employment level of output ((Y_F)), and unemployment has returned to its natural rate. The only permanent effect of the shock is a significantly lower overall price level.
AP Exam Tips & Common Pitfalls
[FRQ Task]: You will frequently be asked to show the short-run effect of a shock and then "explain the long-run adjustment process." To earn full points, you must explicitly state that (1) nominal wages (or input prices) change due to the output gap, (2) this change in costs shifts the SRAS curve, and (3) the economy returns to full-employment output at a new price level.
[MCQ Task]: A common question asks for the long-run impact of an AD shock on the price level and output. Remember that in the long run, output always returns to (Y_F); only the price level changes permanently.
[Common Pitfall ①]: Stopping in the short run. Many students correctly identify the short-run impact of a shock but forget to describe the long-run adjustment. Always ask yourself: "What happens next to wages and input prices because of the new level of unemployment?"
[Common Pitfall ②]: Shifting the wrong curve to adjust. The self-adjustment mechanism works through changes in nominal wages and input costs. Changes in input costs are a determinant of the SRAS curve. Do not shift AD or LRAS to show the economy's automatic return to full employment. The AD curve only shifts back if the initial cause of the shock reverses, and LRAS only shifts if the economy's potential changes.
Key Vocabulary
Long-Run Self-Adjustment: The process through which an economy returns to full employment output in the long run without government intervention, driven by flexible wages and prices.
Recessionary Gap: The condition where short-run equilibrium real GDP is below the full-employment level of output, associated with high unemployment.
Inflationary Gap: The condition where short-run equilibrium real GDP is above the full-employment level of output, associated with very low unemployment.
Flexible Wages and Prices: The long-run assumption that nominal wages and other input prices will fully adjust up or down to match economic conditions, restoring full employment.
Natural Rate of Unemployment: The rate of unemployment that persists when the economy is at its full-employment level of output. It includes only frictional and structural unemployment.