ECON2000 Chap.6 Inflation and Business Cycles
Inflation and Business Cycles
Inflation is the percentage growth of the price level, so disinflation means prices rise more slowly rather than fall. This chapter keeps price levels, inflation rates and expected inflation distinct, then applies the Fisher relationship to nominal and real interest rates.
It uses business-cycle comovement to distinguish demand weakness from adverse supply pressure and explains why consumption tends to move with output while investment is more volatile. The short-run Phillips relationship connects inflation surprises with labour-market slack, while expectations prevent it from becoming a permanent policy menu.
Worked examples calculate inflation and realised real returns, and practice questions diagnose shocks from the joint movement of output, inflation and unemployment.
What this chapter covers
- 01
Price level and inflation
- 02
Disinflation and deflation
- 03
Expected inflation
- 04
Fisher relationship
- 05
Phillips curve
- 06
Output gaps
- 07
Cyclical comovement
Worked example · free
Expected and realised real returns
- +1Expected real return is approximately 6% minus 2%, equal to 4%.
- +2Realised real return is approximately 6% minus 5%, equal to 1%.
- +1Unexpected inflation reduced the lender's purchasing-power return by about 3 percentage points.
- +1The borrower benefited relative to the contracted expectation.
Key terms
- Inflation rate
- The proportional increase in the general price level over a stated period.
- Disinflation
- A reduction in a positive inflation rate, so prices continue rising more slowly.
- Deflation
- A decline in the general price level, represented by a negative inflation rate.
- Fisher relationship
- The approximate link between nominal interest, real interest and expected inflation.
- Phillips curve
- A short-run relationship connecting inflation with unemployment or economic slack under given expectations.
Inflation and Business Cycles FAQ
Does lower inflation mean prices fall?
Not when inflation remains positive. A fall from 6% to 2% is disinflation: the price level continues rising at a slower pace. Prices fall only when the inflation rate becomes negative, which is deflation.
Why does expected inflation affect nominal rates?
Lenders care about the purchasing power repaid. If expected inflation rises while the desired real return is unchanged, they require a higher nominal rate. Unexpected inflation changes the realised real return because the nominal contract was fixed using an earlier expectation.
How can comovement identify a shock?
A negative demand shock normally lowers output and inflation together. An adverse supply shock lowers output but raises inflation. Those patterns help classify the disturbance, although overlapping shocks and policy responses mean comovement alone is not definitive causal evidence.
Why is investment more cyclical than consumption?
Investment depends strongly on financing costs and expected demand, so firms can postpone or cancel projects quickly when conditions weaken. Consumption includes many smoother essential purchases. Investment therefore often moves in the same direction as output but with a larger percentage deviation.
Exam move
Make a vocabulary grid with price level, inflation, disinflation and deflation, and write one numerical example for each. Practise the Fisher approximation using expected inflation for ex-ante real rates and realised inflation for ex-post returns. For cycle questions, list the observed directions of output, inflation, consumption, investment and unemployment before naming a shock.
Redraw the short-run Phillips curve with an explicit expectations label and explain why expectations adjustment shifts the relationship. Finish by checking whether the question reports levels, growth rates or deviations from trend. Many incorrect narratives come from moving between those measures without noticing.
Construct a short price-index series and calculate consecutive inflation rates so a slowing rate can be seen alongside a still-rising level. Compare the approximate Fisher equation with the exact gross-rate relation at modest and high inflation to learn when the interaction term matters.
Create one fixed nominal contract and calculate expected and realised real returns under several inflation outcomes, noting which party gains from the surprise. For business-cycle data, label each variable procyclical, countercyclical or acyclical, then describe its volatility separately. Use output-inflation comovement to form a shock hypothesis before drawing the Phillips or AD-AS picture.
Rehearse how a demand expansion creates a movement along a short-run relationship and how revised inflation expectations shift it later. In every written answer, name the information set for expected inflation and distinguish a temporary cyclical gap from a trend change. This sequence keeps measurement, expectation formation and structural interpretation from being merged into one unsupported claim.
Finish revision by building two timelines. The first follows expected inflation into a nominal contract and then compares realised inflation with the contracted rate. The second follows a demand shock through output, unemployment, inflation and expectations adjustment. Mark which statements concern levels, rates or gaps. If any sentence changes category without explanation, rewrite it.
This catches the usual confusion between disinflation, deflation and a falling relative price.
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