Macroeconomic Equilibrium

IB Economics Higher Level· Unit 3: Macroeconomics, Topic 4· 10 min read

1. Short-Run Macroeconomic Equilibrium★★☆☆☆⏱ 3 min

📘 Definition

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 $A D_{1}$ to $A D_{2}$ .
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.

2. Long-Run Macroeconomic Equilibrium★★★☆☆⏱ 4 min

📘 Definition

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 $A D_{1}$ , $S R A S_{1}$ and $L R A S$ , at $Y_{p}$ and $P_{1}$ .
2
Higher consumer confidence increases consumption, shifting AD right to $A D_{2}$ . 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 $S R A S_{2}$ .
4
The new long-run equilibrium returns output to $Y_{p}$ , at a permanently higher price level $P_{3}$ .

3. Output Gaps★★★☆☆⏱ 3 min

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 ext{$}10 trillion and new short-run equilibrium output is ext{$}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
$\text{Size of recessionary gap} = Y_p - Y_e = 10 - 9.2 = \$0.8 \text{ trillion}$

4. Adjustment to Long-Run Equilibrium★★★★☆⏱ 5 min

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:

Methods compared

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
1. High unemployment means workers accept lower nominal wages, which reduces production costs for all firms.
3
1. Lower production costs shift the SRAS curve rightward.
4
1. The right shift of SRAS moves equilibrium output back to $Y_{p}$ , closing the gap at a lower price level.

5. Common Pitfalls

Wrong move:

Drawing LRAS as upward-sloping like SRAS

Why:

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 move:

Draw LRAS as a vertical line at potential output $Y_{p}$

Wrong move:

Confusing an inflationary gap with inflation itself

Why:

An inflationary gap is an output gap that creates upward pressure for inflation, it is not inflation itself

Correct move:

Define inflationary gap as $Y_{e} > Y_{p}$ , then explain it leads to long-run inflation

Wrong move:

Claiming automatic adjustment closes output gaps by shifting AD

Why:

Automatic adjustment works through changes to production costs that shift SRAS, not AD. AD is shifted by policy intervention

Correct move:

Remember: automatic adjustment → SRAS shifts, policy intervention → AD shifts

Wrong move:

Forgetting to explicitly label the output gap on diagrams

Why:

IB mark schemes require explicit identification of the output gap to access full marks for diagram-based questions

Correct move:

Label the horizontal distance between $Y_{e}$ and $Y_{p}$ as the recessionary or inflationary gap

Wrong move:

Claiming long-run equilibrium always has the same price level

Why:

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 move:

Note that only potential output is fixed in the long run (until LRAS shifts); price level can change freely

6. Quick Reference 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

7. Frequently Asked

Do I need to draw LRAS for all equilibrium questions?

Most IB HL questions require including LRAS to show long-run equilibrium context, unless explicitly asked only for short-run analysis. Always label LRAS to access full marks.

What is the difference between equilibrium output and potential output?

Potential output ( $Y_{p}$ ) is the full-employment output of the economy. Long-run equilibrium always occurs at $Y_{p}$ , but short-run equilibrium can be above or below potential output.

When this came up on past exams

AI-estimated based on syllabus patterns — cross-check with official past papers for accuracy. Use only as revision-focus signals.

2022 · 1
Draw and label a recessionary gap
2023 · 2
Analyze long-run equilibrium adjustment
2021 · 1
Compare two types of output gaps

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.