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Business
Cycles

Understand the rhythmic fluctuations in real GDP: expansions, peaks, contractions, and troughs that define the macroeconomic landscape.

AP Macroeconomics

What Is a Business Cycle?

A business cycle is the periodic rise and fall of real GDP over time. Economies do not grow in a straight line: they alternate between periods of expansion (growth) and contraction (decline).

The Four Phases

Expansion
Real GDP rises, unemployment falls, consumer confidence grows.
Peak
The high point of real GDP before the economy begins to slow down.
Contraction
Real GDP declines, unemployment rises, spending decreases.
Trough
The low point of real GDP before recovery begins again.

Visualizing the Cycle

Time Real GDP Trend Peak Trough Peak Trough Expansion Contraction

Key Indicators of the Cycle

Leading
Stock prices, building permits, consumer expectations: change before GDP shifts.
Coincident
Employment, industrial production, personal income: move with GDP.
Lagging
Unemployment duration, CPI for services, bank lending rates: change after GDP shifts.

Real GDP and the Output Gap

The output gap measures the difference between actual real GDP and potential (full-employment) GDP. It is the central concept linking business cycles to policy.

Positive Gap
\( \text{Actual GDP} > \text{Potential GDP} \): inflationary pressure, economy overheating.
Negative Gap
\( \text{Actual GDP} < \text{Potential GDP} \): recessionary pressure, high unemployment.

AD-AS and Business Cycles

Real GDP Price Level LRAS SRAS
\(AD_1\)
\(AD_2\)
 Gap

Expansion vs. Contraction

Expansion Contraction
Real GDP Rising Falling
Unemployment Decreasing Increasing
Consumer Spending Growing Shrinking
Inflation Pressure Rising Falling
Business Investment Increasing Decreasing

Why Do Cycles Happen?

1
Demand shocks: Sudden changes in consumer spending, investment, government purchases, or net exports shift AD left or right.
2
Supply shocks: Events like oil price spikes or natural disasters shift SRAS, causing stagflation or cost-push changes.
3
Monetary policy: The Federal Reserve raises or lowers interest rates, expanding or contracting the money supply.
4
Fiscal policy: Government changes in taxation and spending directly alter aggregate demand.

How to Identify the Phase

1
Check real GDP direction: Is it increasing (expansion) or decreasing (contraction)?
2
Look at unemployment: Falling unemployment signals expansion; rising signals contraction.
3
Assess inflation trends: Accelerating inflation suggests a peak approaching; deflation signals a trough.
4
Compare to potential GDP: Positive output gap = past the peak; negative output gap = near the trough.
5
Use leading indicators: Stock market trends, building permits, and new orders signal future direction.

Example: Identifying a Recession

Suppose real GDP was \$18.5 trillion in Q1, \$18.2 trillion in Q2, and \$17.9 trillion in Q3. The unemployment rate rose from 4.2% to 5.8% over the same period.

Example: Calculating the Output Gap

Potential GDP is \$20 trillion. Actual GDP is \$19 trillion. What is the output gap?

Example: Policy Response

The economy is in a recessionary gap. The Federal Reserve decides to lower the federal funds rate. Congress passes a stimulus bill increasing government spending.

1
Monetary policy: Lower interest rates increase borrowing and investment, shifting AD right.
2
Fiscal policy: Higher government spending directly adds to GDP and shifts AD right.
3
Combined effect: Real GDP rises toward potential, unemployment falls, and the economy moves from contraction into expansion.

Common Mistakes

✕ Confusing recession with depression
A recession is 2+ quarters of GDP decline. A depression is a severe, prolonged recession: much rarer and more extreme.
✕ Mixing up leading and lagging
Students often call unemployment a leading indicator. It is lagging: it rises after a contraction begins and falls after recovery starts.
✕ Peak = best economy
The peak is a turning point, not the "healthiest" state. At the peak, inflation is often high and a contraction is imminent.

Business Cycle Summary

Phase GDP Unemployment Inflation
Expansion Rising Falling Rising
Peak Maximum Lowest Highest
Contraction Falling Rising Falling
Trough Minimum Highest Lowest

Question 1 of 5

A recession is officially defined as a decline in real GDP lasting:

Question 2 of 5

Which of the following is a leading economic indicator?

Question 3 of 5

If actual GDP is \$22 trillion and potential GDP is \$20 trillion, the economy is experiencing:

Question 4 of 5

During the contraction phase of a business cycle, which of the following is most likely to occur?

Question 5 of 5

A government increases spending and the central bank lowers interest rates simultaneously. This combination of policies is designed to close a: