# Macroeconomic Equilibrium

> IB Economics Higher Level · IB DP Economics
> Source: https://www.owlsprep.com/study/ib-economics-hl-u3-macroeconomic-equilibrium/

This sub-topic explains how aggregate demand and aggregate supply interact to determine equilibrium output and price levels in the short and long run, and how the economy adjusts to output gaps.

**Prerequisites:** [Aggregate Demand (AD)](https://www.owlsprep.com/study/ib-economics-hl-u3-aggregate-demand/); [Aggregate Supply (AS)](https://www.owlsprep.com/study/ib-economics-hl-u3-aggregate-supply/)

## Learning objectives

- Define short-run and long-run macroeconomic equilibrium
- Illustrate equilibrium on AD-AS diagrams
- Analyze the two types of output gaps
- Evaluate mechanisms to adjust to long-run equilibrium

## Short-Run Macroeconomic Equilibrium

**Short-run macroeconomic equilibrium** — Occurs when aggregate demand (AD) equals short-run aggregate supply (SRAS), determining the equilibrium price level and equilibrium real output.

*Example:* At equilibrium price $P_e$, the total quantity of output demanded by households, firms and government equals the total quantity supplied by firms in the short run.

In the short run, nominal wages and output prices are sticky, so equilibrium is determined purely by the intersection of AD and SRAS. Any shift in AD or SRAS will change both the equilibrium price level and equilibrium real output.

**Worked example:** A government increases infrastructure spending. Show how this impacts short-run equilibrium output and the price level.

1. Government spending is a component of AD, so the AD curve shifts rightward from $AD_1$ to $AD_2$.
2. The new intersection of AD and SRAS occurs at a new equilibrium:
3. $$Y_2 > Y_1 \quad \text{and} \quad P_2 > P_1$$

> **Exam tip:** Always label all curves, axes and equilibrium points clearly in AD-AS diagrams to gain full marks.

## Long-Run Macroeconomic Equilibrium

**Long-run macroeconomic equilibrium** — Occurs when aggregate demand equals short-run aggregate supply *and* equals long-run aggregate supply (LRAS). Equilibrium output equals potential full-employment output ($Y_p$).

*Example:* At long-run equilibrium, there is no cyclical unemployment, and the economy operates at its maximum sustainable output.

LRAS is vertical at potential output because in the long run, all wages and prices are fully flexible, so the level of output is independent of the price level. Changes in AD only affect the price level, not long-run equilibrium output.

**Worked example:** An economy starts at long-run equilibrium. A permanent increase in consumer confidence shifts AD right. What is the new long-run equilibrium?

1. Initial long-run equilibrium is the intersection of $AD_1$, $SRAS_1$ and $LRAS$, at $Y_p$ and $P_1$.
2. Higher consumer confidence increases consumption, shifting AD right to $AD_2$. In the short run, equilibrium is at $Y_2 > Y_p$, $P_2 > P_1$, creating an inflationary gap.
3. In the long run, nominal wages adjust to higher prices, increasing firm production costs and shifting SRAS left to $SRAS_2$.
4. The new long-run equilibrium returns output to $Y_p$, at a permanently higher price level $P_3$.

## Output Gaps

When short-run equilibrium output does not equal potential output, the economy experiences an output gap. There are two distinct types of output gaps:

- **Recessionary (deflationary) gap**: Short-run equilibrium output ($Y_e$) < potential output ($Y_p$), associated with cyclical unemployment above the natural rate.
- **Inflationary (expansionary) gap**: Short-run equilibrium output ($Y_e$) > potential output ($Y_p$), associated with upward pressure on prices (inflation).

**Worked example:** A fall in business investment shifts AD left. If potential output is \text{\$}10 trillion and new short-run equilibrium output is \text{\$}9.2 trillion, identify and calculate the output gap.

1. A fall in investment reduces AD, leading to short-run equilibrium below potential output, so this is a recessionary gap.
2. $$\text{Size of recessionary gap} = Y_p - Y_e = 10 - 9.2 = \$0.8 \text{ trillion}$$

## Adjustment to Long-Run Equilibrium

Output gaps are only temporary in the long run. There are two main approaches to returning the economy to long-run equilibrium at potential output:

**Comparing methods**

- **Automatic Market Adjustment** — Wages and prices adjust freely over time. For a recessionary gap, high unemployment lowers nominal wages, shifting SRAS right. For an inflationary gap, higher prices raise nominal wages, shifting SRAS left.
  - Pros: No government intervention, avoids policy lags and errors
  - Cons: Adjustment is slow, leading to prolonged high unemployment or inflation

- **Policy Intervention** — Governments use fiscal policy and central banks use monetary policy to shift AD to close gaps. Expansionary policy shifts AD right to close recessionary gaps; contractionary policy shifts AD left to close inflationary gaps.
  - Pros: Faster adjustment reduces economic instability
  - Cons: Policy lags, crowding out, and unintended side effects like inflation

**Worked example:** Show how automatic adjustment closes a recessionary gap.

1. 1. A recessionary gap has $Y_e < Y_p$, so cyclical unemployment is above the natural rate.
2. 2. High unemployment means workers accept lower nominal wages, which reduces production costs for all firms.
3. 3. Lower production costs shift the SRAS curve rightward.
4. 4. The right shift of SRAS moves equilibrium output back to $Y_p$, closing the gap at a lower price level.

## Common pitfalls

- **Wrong:** Drawing LRAS as upward-sloping like SRAS
  - Why it fails: LRAS is vertical at potential output because all wages and prices are fully flexible in the long run, so output is independent of the price level
  - Correct: Draw LRAS as a vertical line at potential output $Y_p$
- **Wrong:** Confusing an inflationary gap with inflation itself
  - Why it fails: An inflationary gap is an output gap that creates upward pressure for inflation, it is not inflation itself
  - Correct: Define inflationary gap as $Y_e > Y_p$, then explain it leads to long-run inflation
- **Wrong:** Claiming automatic adjustment closes output gaps by shifting AD
  - Why it fails: Automatic adjustment works through changes to production costs that shift SRAS, not AD. AD is shifted by policy intervention
  - Correct: Remember: automatic adjustment → SRAS shifts, policy intervention → AD shifts
- **Wrong:** Forgetting to explicitly label the output gap on diagrams
  - Why it fails: IB mark schemes require explicit identification of the output gap to access full marks for diagram-based questions
  - Correct: Label the horizontal distance between $Y_e$ and $Y_p$ as the recessionary or inflationary gap
- **Wrong:** Claiming long-run equilibrium always has the same price level
  - Why it fails: Long-run equilibrium always occurs at potential output, but shifts in AD or SRAS change the equilibrium price level even when output stays at $Y_p$
  - Correct: Note that only potential output is fixed in the long run (until LRAS shifts); price level can change freely

## Cheatsheet

| Equilibrium Type | Intersection | Output Level | Key Feature |
| --- | --- | --- | --- |
| Short-run | AD = SRAS | $Y_e \neq Y_p$ | Sticky prices, output gaps possible |
| Long-run | AD = SRAS = LRAS | $Y_e = Y_p$ | Full employment, no output gap |
| Recessionary Gap | AD/SRAS intersect left of LRAS | $Y_e < Y_p$ | Cyclical unemployment present |
| Inflationary Gap | AD/SRAS intersect right of LRAS | $Y_e > Y_p$ | Upward inflation pressure |

## What's next

Understanding macroeconomic equilibrium is the foundation for analyzing how fiscal and monetary policy work to stabilize the economy, and how economic shocks impact growth and unemployment. This framework is used in almost all IB HL macroeconomics essay and data response questions, so mastering equilibrium diagram analysis is critical for high marks. Next, you will explore how policymakers respond to output gaps, and how long-run economic growth shifts potential output over time. This concept also connects directly to topics like unemployment and inflation, where output gaps explain short-run changes in these key macroeconomic indicators.

- [Fiscal Policy](https://www.owlsprep.com/study/ib-economics-hl-u3-fiscal-policy/)
- [Monetary Policy](https://www.owlsprep.com/study/ib-economics-hl-u3-monetary-policy/)
- [Economic Growth](https://www.owlsprep.com/study/ib-economics-hl-u3-economic-growth/)

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