CA Foundation · Business Economics

Business Cycles: formula sheet

Full chapter guide

Key formulas

Core definition: Business cycle = recurrent fluctuations in aggregate economic activity around the long-term growth trend; Say 'aggregate' and 'recurrent'. Do not describe it as a change in one industry.
Periodicity rule: Recurrent ≠ periodic; Cycles repeat, but their length and size are irregular.
Phase sequence: Expansion → Peak → Contraction → Trough → Expansion; Phases are covered in detail in a separate topic. Know the order here.
Order of phases: Expansion → Peak → Contraction (Recession) → Trough → Recovery → Expansion; Recovery is the upturn from the trough. Some books treat it as part of expansion, so read the question wording carefully.
Peak-to-trough: Contraction = movement from peak down to trough; Expansion (including recovery) is the movement from trough up to peak.
Recession rule of thumb: Recession ≈ real GDP falls for 2 consecutive quarters; A common working rule, not an exact definition used everywhere. Depression is a far more severe and prolonged downturn.
Direction of key variables: Expansion: output ↑, employment ↑, income ↑, demand ↑; Contraction: all ↓; Prices and profits generally move in the same direction as output over the cycle.
Recurrent but not periodic: Cycles repeat (recurrent) ≠ cycles repeat at fixed intervals (periodic); Length and intensity vary from one cycle to the next. Exact timing cannot be forecast.
Synchronization: Output, employment, income, sales, profits move together across sectors; Shows business cycles are economy-wide, not confined to one industry.
Pervasiveness: Cycle spreads from one sector or country to others; Linked through inter-industry purchases and, in open economies, through trade.
Uneven impact: Fluctuation: durable goods and investment goods > non-durable goods and services; Durable purchases and capital spending can be postponed, so they swing more.
Internal (endogenous) causes: Demand + Investment + Money/credit + Policy + Expectations; These arise inside the economic system. Remember as the economy's own working.
External (exogenous) causes: Wars + Technology + Weather + Political events + Oil/global shocks; These arise outside the economic system and act as shocks.
Classification test: Originates within the economy → endogenous; imposed from outside → exogenous; Use this to classify any option in one step.
Multiplier: k = ΔY ÷ ΔI = 1 ÷ (1 − MPC); MPC is the marginal propensity to consume. A higher MPC gives a larger multiplier.
Accelerator: Investment ≈ v × ΔY, where v = capital-output ratio; Induced investment depends on the change in income or output, not its level.
Theory to cause match: Hawtrey → credit; Keynes → investment and expectations; Schumpeter → innovation; Samuelson → multiplier + accelerator; RBC → real (technology) shocks; Use this one-line map to answer most theory-matching MCQs.
Real GDP growth rate: Growth rate (%) = (Real GDP this year − Real GDP last year) ÷ Real GDP last year × 100; Use real GDP, not nominal, so price changes do not distort the cycle reading.
Recession rule of thumb: Two or more consecutive quarters of falling real GDP ⇒ recession; A popular rule of thumb, not an exact definition used everywhere.
Leading indicator: Turns BEFORE the economy turns; Used for forecasting. Examples: new orders, stock prices, building permits.
Coincident indicator: Turns AT THE SAME TIME as the economy; Shows the current state. Examples: industrial production, employment, personal income.
Lagging indicator: Turns AFTER the economy turns; Confirms a turning point. Examples: unemployment rate, lending rates. CPI (especially services inflation) is generally treated as lagging, but sources differ.
Typical phase effects: Expansion: output ↑, jobs ↑, prices ↑, investment ↑. Recession: output ↓, jobs ↓, inflation ↓, investment ↓; Investment swings most. Essentials swing less than durables.
Recession rule (expansionary policy): Recession → ↑ Govt spending, ↓ Taxes, ↓ Interest rates, ↑ Money supply; Aim is to raise aggregate demand, output and employment.
Boom or inflation rule (contractionary policy): Boom/inflation → ↓ Govt spending, ↑ Taxes, ↑ Interest rates, ↓ Money supply; Aim is to reduce aggregate demand and cool prices.
Monetary tools direction: Expansionary: ↓ Repo, ↓ CRR, buy securities. Contractionary: ↑ Repo, ↑ CRR, sell securities; Open market operations: buying injects money, selling withdraws it.
Budget stance: Recession → deficit budget; Boom → surplus or lower-deficit budget; Fiscal stance is judged by the direction of the change, not just the sign of the balance.

Quick revision

A business cycle is a recurring fluctuation in overall economic activity, not a single event.
The phases are expansion, peak, contraction (recession) and trough, followed by recovery.
In expansion, output, employment, income and demand rise.
At the peak, activity is highest and pressure on resources and prices is greatest.
In contraction, output, employment and demand fall.
At the trough, activity is at its lowest point before recovery begins.
Cycles recur but are not of fixed length or equal strength.
Cycles are usually seen across many sectors together, not in one industry alone.
Causes may be internal to the economy or external shocks; match each cause to its type.
Learn each named theory with its single main idea so you can match it in a question.
Fiscal policy uses government spending and taxes; monetary policy uses money supply and interest rates.
In a slowdown, policy aims to raise demand; in a boom with rising prices, it aims to cool demand.

Common mistakes

Saying business cycles are periodic and repeat at fixed intervals. Fix: Remember: recurrent but not periodic. Length and intensity differ from cycle to cycle.
Treating a fall in one industry's output as a business cycle. Fix: Look for aggregate indicators: real GDP, employment, income. One sector alone is not a cycle.
Confusing peak with trough. Fix: Peak is the highest activity and the turn to decline. Trough is the lowest activity and the turn to growth.
Treating recession and depression as the same thing. Fix: Recession is a downturn phase of the cycle. Depression is an extremely severe, prolonged downturn with very high unemployment.
Treating 'recurrent' and 'periodic' as the same word. Fix: Recurrent means it keeps happening. Periodic means it happens at fixed intervals. Business cycles are the first, not the second.
Believing a business cycle affects only one industry. Fix: Remember synchronization and pervasiveness: the effect spreads across sectors because they depend on each other.
Calling monetary factors an external cause because the central bank is outside firms. Fix: Money supply, credit and interest rates are part of the economy's own working, so treat them as internal.
Treating technology as always internal. Fix: In this classification, technology shocks and major innovations are listed as external causes. Follow that grouping in exams.
Mixing up Keynes and Samuelson because both use the multiplier. Fix: Keynes stresses expectations and investment changes. Samuelson specifically needs the multiplier and accelerator working together.
Saying Hawtrey's theory is about innovation or real factors. Fix: Link Hawtrey with credit, bank reserves and money flow. It is a monetary theory.

Exam tips

Memorise the phrase 'recurrent but not periodic'. It is the most frequently tested point.
Watch for absolute words such as 'always', 'fixed' and 'only'. They usually signal a wrong option.
Know the difference between aggregate activity and a single sector, and between cycles and seasonal variation.
Remember the phase order: expansion, peak, contraction, trough. Questions may combine meaning with phases.
If you cannot decide between two options, skip. Negative marking is 0.25 per wrong answer.
Most questions test recognition: read the clue words (lowest, highest, rising, falling) before looking at options.
Watch for options that scramble the sequence. Write the correct order on rough paper first.
Recession versus depression is a favourite distinction: remember severity and duration.