The business cycle describes short-run fluctuations in real GDP and employment around potential output. These fluctuations are driven by changes in aggregate demand and/or aggregate supply. Knowing the four features of the cycle, its phases, turning points, and the output gap, is essential for interpreting economic data and connecting to policy in later units.
- Expansion: The phase when real GDP is rising. Employment increases and unemployment falls toward the natural rate.
- Recession: The phase when real GDP is falling. Unemployment rises above the natural rate as cyclical unemployment increases.
- Peak and trough: The peak is the turning point where expansion ends and recession begins. The trough is where recession ends and expansion begins.
- Output gap: The difference between actual real GDP and potential (full-employment) output. A negative gap is a recessionary gap; a positive gap is an inflationary gap.
- Potential output: The level of real GDP produced when unemployment equals the natural rate. Also called full-employment output.
Draw a business cycle graph. Label the expansion, recession, peak, trough, and potential output line. Then identify where a recessionary gap and an inflationary gap would appear.
| Feature | Recessionary gap | Inflationary gap |
|---|
| Actual vs. potential output | Actual < Potential | Actual > Potential |
| Unemployment vs. natural rate | Unemployment > Natural rate | Unemployment < Natural rate |
| Cyclical unemployment | Positive | Negative (overemployment) |
| Business cycle phase | Recession or early recovery | Late expansion |