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Inflation and Deflation: Causes, Effects and Measurement for ACCA BT

Updated 11 October 2026 · Fact-checked

Inflation is a sustained rise in the general price level, so money buys less over time. Deflation is a sustained fall in that level. In BT, identify the cause (demand-pull or cost-push), then state the effects on businesses, consumers and the economy. Measure it using price indices such as CPI or RPI.

Understand Inflation and Deflation

Inflation is a sustained increase in the general level of prices in an economy. It is not one price rising. It is prices in general rising over time. The value of money falls, so each unit of currency buys fewer goods. The inflation rate is the percentage change in a price index over a period, usually a year.

Demand-pull inflation happens when total demand in the economy grows faster than the economy's ability to supply goods and services. Too much spending chases too few goods, so sellers raise prices. Typical triggers are tax cuts, lower interest rates, rising consumer confidence, higher government spending or rapid growth in the money supply.

Cost-push inflation happens when the costs of production rise and firms pass them on as higher prices. Typical triggers are higher wages not matched by productivity, higher raw material or energy prices, higher import prices after a currency fall, and higher taxes on business. Demand does not have to rise. The push comes from the supply side.

Inflation is measured with a price index. A Consumer Prices Index (CPI) tracks the cost of a fixed basket of goods and services bought by typical households. A Retail Prices Index (RPI) is an older UK-style measure, also based on a basket, and it includes some items such as housing costs that CPI treats differently. Baskets are reviewed so they reflect what people actually buy. Exact methods differ by country, so do not quote details beyond the basket idea.

Deflation is a sustained fall in the general price level, meaning the inflation rate is negative. It is different from disinflation, where prices still rise but more slowly. Deflation can be caused by weak demand, falling costs, or strong productivity gains. Weak demand is the harmful kind. Consumers delay purchases expecting lower prices, firms cut output and jobs, and the debt burden grows in real terms.

Key formulas to remember

Inflation rate
Inflation rate (%) = (Price index now − Price index a year ago) ÷ Price index a year ago × 100
A negative result means deflation. A smaller positive result than last year means disinflation.
Real value of money
Real value = Money amount ÷ Price index × 100
Use when comparing amounts across years. Index base year = 100.
Real interest rate (approximate)
Real interest rate ≈ Nominal interest rate − Inflation rate
If inflation is higher than the nominal rate, the real rate is negative and savers lose purchasing power.
Demand-pull test
Demand-pull: aggregate demand rises faster than supply capacity
Look for rising spending, low interest rates, tax cuts, and low unemployment.
Cost-push test
Cost-push: production costs rise and are passed on in prices
Look for wage rises, commodity prices, energy costs, and weaker currency raising import costs.

How to solve Inflation and Deflation questions

Use this method for any BT question on inflation or deflation, whether it is a multiple choice item or a short scenario.

  1. 1Read the scenario and spot the keyword: prices rising, prices falling, costs, demand, wages, currency or index.
  2. 2Decide if prices are rising (inflation), rising more slowly (disinflation) or falling (deflation).
  3. 3If inflation, ask where the pressure comes from. Spending rising points to demand-pull. Input costs rising points to cost-push.
  4. 4Check whether the question asks for cause, effect or measurement. Answer only that.
  5. 5For effects, name who is affected: consumers, savers, borrowers, businesses, workers, government or the economy.
  6. 6For calculations, apply the index formula carefully and check the sign of the answer.
  7. 7Eliminate options that mix up terms, such as calling a fall in the inflation rate deflation.

Quickest way: Cause and effect sort

When to use it: Use for objective test items where you have about a minute and need to classify a cause or an effect.

  1. Underline what changed first in the scenario: demand or cost.
  2. Demand first means demand-pull. Cost first means cost-push.
  3. For deflation, check whether prices are falling or only rising more slowly.
  4. For effects, ask who gains and who loses: borrowers gain from inflation, savers lose.
  5. Choose the option that matches exactly, not one that is only partly true.

Common mistakes in Inflation and Deflation

  • Calling falling inflation 'deflation'.

    Both involve something falling, so the words blur.

    Fix: Deflation means prices actually fall (negative inflation rate). If prices still rise, only more slowly, it is disinflation.

  • Labelling a wage rise as demand-pull.

    Higher wages also raise spending, so it seems like demand.

    Fix: If the question stresses wages as a cost to firms passed into prices, choose cost-push. Choose demand-pull only if the focus is excess spending.

  • Saying inflation harms everyone equally.

    Students remember only that prices rise.

    Fix: State who loses (savers, people on fixed incomes, lenders at fixed rates) and who may gain (borrowers with fixed-rate debts, owners of real assets).

  • Treating deflation as always good because prices fall.

    Lower prices look attractive to consumers.

    Fix: Explain the risk: delayed spending, falling profits, job losses and a heavier real debt burden.

  • Mixing up the price index and the inflation rate.

    Both are quoted as numbers.

    Fix: The index is a level (such as 108). The inflation rate is the percentage change in that level between two dates.

Worked examples

Example 1

A country's consumer price index was 125.0 last year and is 130.0 this year. Calculate the inflation rate.

Show the solution
  1. Find the change in the index: 130.0 − 125.0 = 5.0.
  2. Divide by last year's index: 5.0 ÷ 125.0 = 0.04.
  3. Multiply by 100 to get a percentage: 0.04 × 100 = 4%.

Answer: The inflation rate is 4%.

Example 2

A government cuts income tax and the central bank lowers interest rates. Consumer spending rises sharply. The economy is already near full capacity and prices rise across most sectors. Identify the type of inflation and explain one effect on businesses.

Show the solution
  1. Spot the trigger: tax cuts and lower interest rates increase spending, so aggregate demand rises.
  2. Note that the economy is near full capacity, so supply cannot expand quickly. Prices therefore rise.
  3. This is demand-pull inflation.
  4. Effect on business: input costs and wage demands may rise, which squeezes margins if firms cannot raise their own prices. Planning and pricing also become harder because future costs are uncertain.

Answer: Demand-pull inflation, because rising demand outpaces supply capacity. One effect is higher costs and wage claims, which can reduce margins and make planning less certain.

Exam tips

  • Match the keyword: demand or spending rising means demand-pull, costs or inputs rising means cost-push.
  • In multiple response items, tick only the number of options stated and check each against the exact definition.
  • For number entry, compute the percentage change using the earlier year as the base, and keep the sign.
  • Learn at least three effects of inflation and three of deflation, each tied to a named group such as savers, borrowers or exporters.
  • Do not quote country-specific index details. Describe CPI and RPI as basket-based price indices.

Practice questions from Macroeconomic factors

Inflation and Deflation in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Inflation and Deflation: frequently asked questions

What is the difference between demand-pull and cost-push inflation?

Demand-pull comes from total spending growing faster than the economy can supply, so firms raise prices. Cost-push comes from rising production costs, such as wages or raw materials, that firms pass on. Ask whether demand or costs moved first.

What is the difference between inflation and deflation?

Inflation is a sustained rise in the general price level, so money loses value. Deflation is a sustained fall in that level. If prices rise more slowly than before, that is disinflation, not deflation.

What are the effects of inflation on businesses?

Costs rise and uncertainty makes planning and pricing harder. Firms may face wage claims and need to update prices more often. Borrowers with fixed-rate debt can gain, while cash held loses real value.

How is inflation measured, CPI or RPI?

Both track the cost of a basket of goods and services over time. The inflation rate is the percentage change in the index. They differ in which items are included and how they are calculated.