⚖️ Equilibrium and Changes in Equilibrium
(in the context of Aggregate Demand and Aggregate Supply in Macroeconomics)
🧠 1. What is Macroeconomic Equilibrium?
In macroeconomics, equilibrium occurs when Aggregate Demand (AD) equals Aggregate Supply (AS).
✅ Definition:
Macroeconomic equilibrium is the point where the total quantity of goods and services demanded equals the total quantity of goods and services supplied in the economy at a particular price level.
It determines:
- The equilibrium price level (overall price level in the economy)
- The equilibrium real GDP (actual output or national income)
🪙 Graphical Representation
- Vertical axis: Price level
- Horizontal axis: Real GDP (output)
- AD curve: Downward sloping (as price level ↓, demand ↑)
- SRAS curve: Upward sloping (as price level ↑, supply ↑)
The point where AD intersects SRAS is the short-run equilibrium.
📈 2. Short-Run vs Long-Run Equilibrium
🔹 Short-Run Equilibrium
- Occurs where AD intersects SRAS.
- The economy may not be at full employment.
- Can result in recessionary gap or inflationary gap.
🔹 Long-Run Equilibrium
- Occurs where AD = SRAS = LRAS.
- The economy is producing at full employment output (potential GDP).
- No output gap (unemployment is at the natural rate).
🔁 3. Changes in Equilibrium
When AD or AS shifts, the equilibrium output and price level also change.
🟢 A. Change in Aggregate Demand (AD)
✅ AD Increases (shifts right):
- Equilibrium price level rises (inflation)
- Equilibrium real GDP increases
- Unemployment ↓
- Risk of demand-pull inflation
❌ AD Decreases (shifts left):
- Equilibrium price level falls
- Equilibrium real GDP falls
- Unemployment ↑
- Risk of recession
🔵 B. Change in Short-Run Aggregate Supply (SRAS)
✅ SRAS Increases (shifts right):
- Price level falls
- Real GDP rises
- Unemployment ↓
- Usually due to improved productivity or lower input costs
❌ SRAS Decreases (shifts left):
- Price level rises (cost-push inflation)
- Real GDP falls
- Unemployment ↑
- Often caused by negative supply shocks (e.g., oil price spike)
🟡 C. Change in Long-Run Aggregate Supply (LRAS)
✅ LRAS Increases (shifts right):
- Economic growth
- Higher potential GDP
- Long-run output increases without increasing inflation
❌ LRAS Decreases (shifts left):
- Decline in productive capacity
- May be caused by war, natural disasters, or loss of labor force
📊 Summary Table
| Change |
Price Level |
Output (Real GDP) |
Unemployment |
| ↑ AD |
↑ |
↑ |
↓ |
| ↓ AD |
↓ |
↓ |
↑ |
| ↑ SRAS |
↓ |
↑ |
↓ |
| ↓ SRAS |
↑ |
↓ |
↑ |
| ↑ LRAS |
No change (long-run) |
↑ |
↓ (in long term) |
💡 Real-World Example
🦠 COVID-19 Pandemic (2020):
- AD dropped sharply due to lockdowns and fear → ↓ GDP, ↑ unemployment
- Governments increased spending and central banks lowered interest rates to boost AD → equilibrium slowly restored
🛢️ Oil Price Shock (1970s):
- SRAS decreased due to higher input costs → stagflation (↓ GDP, ↑ inflation, ↑ unemployment)
✅ Key Takeaways
- Equilibrium occurs where AD = AS.
- Changes in AD or AS shift the equilibrium output and price level.
- Short-run equilibrium may differ from full employment.
- Policy tools (fiscal and monetary) aim to restore or maintain equilibrium.