Long-Run Self-Adjustment in the AD-AS Model, Explained

Long-run self-adjustment is the process by which an economy with an output gap returns to full-employment output on its own, with no fiscal or monetary policy, because nominal wages and other input prices eventually change and shift the short-run aggregate supply (SRAS) curve. In a recessionary gap SRAS shifts right and the economy ends at potential output with a lower price level; in an inflationary gap SRAS shifts left and the economy ends at potential output with a higher price level. This guide covers both cases, a worked example, and the AP exam mistakes for CED Topic 3.7.

The three curves you need

Self-adjustment happens on the standard AD-AS graph. For a full refresher, read the AD-AS model explained.

• Aggregate demand (AD) slopes downward.
• Short-run aggregate supply (SRAS) slopes upward because nominal wages and some input prices are fixed in the short run.
• Long-run aggregate supply (LRAS) is vertical at full-employment (potential) output.

Short-run equilibrium is where AD crosses SRAS; long-run equilibrium is where all three intersect. When short-run equilibrium sits left or right of LRAS, the economy has an output gap. For a side-by-side of the two supply curves, see SRAS vs LRAS.

Closing a recessionary gap

A recessionary gap exists when short-run equilibrium output is below full-employment output. It often starts with a leftward AD shift, such as a drop in consumer confidence.

1. Output is below potential, so firms need fewer workers and unemployment rises above the natural rate of unemployment.

2. With many workers competing for scarce jobs, nominal wages and other input prices fall over time as contracts are renegotiated.

3. Lower input costs make production cheaper at every price level, so SRAS shifts to the right.

4. As SRAS shifts right, the economy moves down along the existing AD curve. The price level falls and real GDP rises.

5. SRAS keeps shifting until it crosses AD at LRAS. Output is back at potential and unemployment is back at the natural rate, but the price level is lower than it was before the shock.

Notice what did not move. AD stays where the shock left it, and LRAS does not move at all. The only curve that shifts during self-adjustment is SRAS.

Closing an inflationary gap

An inflationary gap exists when short-run output is above full-employment output, often after a rightward AD shift.

1. Output is above potential, so the labor market is tight and unemployment is below the natural rate.

2. Firms compete for scarce workers, and workers notice prices rising, so nominal wages and input prices rise over time.

3. Higher costs shift SRAS to the left.

4. The economy moves up along AD: the price level rises and real GDP falls.

5. SRAS stops shifting where it crosses AD at LRAS. Output returns to potential at a higher price level.

The two cases mirror each other in mechanism, though not in speed (see below). In both, the economy finishes on the vertical LRAS line with real GDP and unemployment back where they started; what has changed is the price level, along with the nominal wages behind it.

Why LRAS stays put

LRAS reflects the economy's labor, capital, natural resources, and technology. A change in nominal wages changes what it costs to produce output, which is an SRAS shifter, but it creates no new workers, machines, or technology. So LRAS is the anchor the economy returns to, and it shifts only when productive capacity itself changes.

A worked numerical example

Suppose an economy's full-employment output is $1,000 billion of real GDP, and it starts in long-run equilibrium at a price level of 110.

Recessionary gap. A fall in consumer confidence shifts AD left. The new short-run equilibrium is real GDP of $950 billion at a price level of 105. Output is $50 billion below potential, a recessionary gap equal to 5 percent of potential output. Nominal wages fall, SRAS shifts right, and the economy slides down the new AD curve until it reaches $1,000 billion at a price level of 100.

Inflationary gap. Start again from $1,000 billion at a price level of 110. This time a surge in business investment shifts AD right, and the new short-run equilibrium is $1,050 billion at a price level of 115. That is a $50 billion inflationary gap. Nominal wages rise, SRAS shifts left, and the economy climbs the new AD curve until it reaches $1,000 billion at a price level of 120.

During the recession's adjustment, real GDP rises from 950 to 1,000 while the price level falls from 105 to 100, a movement down along AD. During the boom's adjustment, real GDP falls from 1,050 to 1,000 while the price level rises from 115 to 120, a movement up along AD. Final real GDP equals starting real GDP because LRAS never moved.

You can rehearse both cases yourself on the interactive AD-AS graph: shift AD, read off the gap, then shift SRAS until the intersection lands on LRAS.

See it move

Make it move

The AD-AS model in long-run equilibrium at full-employment output. Tap it to drag the curves, open the full version, or put it on your own site free, or turn it into a five-minute class activity.

Why self-adjustment is slow

The adjustment depends on nominal wages and prices changing, and those are sticky. Wages are often set by contracts lasting a year or more, employers avoid pay cuts that hurt morale, and workers resist nominal pay cuts. This is the logic behind the sticky-wage theory of SRAS. Many output prices are also reset only occasionally, which slows the adjustment further.

Wages tend to be stickier downward than upward, so a recessionary gap can persist for a long time, with high unemployment and lost output the entire while.

The case for stabilization policy

The slowness of self-adjustment is the core of the policy debate in AP Macro Unit 3.

• The classical view trusts flexible wages and prices to close gaps reasonably quickly, so policymakers should mostly let the economy correct itself.
• The Keynesian view argues that sticky wages make the wait too costly. Keynes put it bluntly: in the long run we are all dead. Instead of waiting for SRAS to shift, the government can shift AD back toward LRAS with fiscal policy, or the central bank can use monetary policy.

On the graph, expansionary policy closes a recessionary gap at roughly the original price level, while self-adjustment closes it at a lower one. Both end on LRAS.

How the AP exam tests it

Self-adjustment questions start with an output gap and tell you to assume no policy action, or ask what happens in the long run. Expect tasks like these:

• Explain the wage change. In a recessionary gap, nominal wages fall because unemployment is above the natural rate. In an inflationary gap, nominal wages rise because unemployment is below the natural rate.
• Name the curve and direction. SRAS shifts right in a recessionary gap and left in an inflationary gap.
• Draw the adjustment. Shift SRAS so that the new SRAS curve crosses the existing AD curve exactly at LRAS. Label the new curve (for example SRAS₂), the new price level, and show that output equals full-employment output.
• State the outcomes. Real GDP returns to potential, unemployment returns to the natural rate, and the price level ends lower (recessionary) or higher (inflationary) than in the short-run equilibrium.

The Topic 3.7 study page has a compact summary.

Common mistakes

• Shifting AD instead of SRAS. Self-adjustment works through production costs. If the question says no policy is taken, leave AD alone.
• Moving LRAS. Wage changes do not change productive capacity. LRAS stays put, and it is the line the economy returns to.
• Getting the price level direction wrong. A recessionary gap closes at a lower price level; an inflationary gap closes at a higher one. A quick check: SRAS shifting right lowers the price level, and SRAS shifting left raises it.
• Mixing up nominal and real wages. The AP answer is that nominal wages fall in a recession and rise in a boom. That nominal change is what shifts SRAS.
• Stopping the shift in the wrong place. The new SRAS has to cross AD on the LRAS line. A drawing where the new intersection lands left or right of LRAS has not finished adjusting.

If a question shifts both AD and SRAS at once, the reasoning changes; see AD-AS shift combinations for every case.