2.1.2 - Inflation

Understanding Inflation

Students often confuse inflation with any single price rise. In economics, inflation means a sustained rise in the general price level across the economy, not just one product becoming more expensive.

If the price of coffee rises after a poor harvest, that does not by itself mean the economy has inflation. Inflation is about prices in general rising over time.

Deflation is a sustained fall in the general price level. Disinflation is different again: it means the rate of inflation is falling, so prices are still rising, but more slowly than before. If inflation falls from 6% to 3%, that is disinflation. If inflation falls from 2% to -1%, the economy has moved into deflation.

Measuring Inflation

In the UK, inflation is usually measured using the Consumer Prices Index, or CPI. This tracks the average change in the price of a representative basket of goods and services bought by households.

The Office for National Statistics chooses hundreds of items for the basket and updates it every year so it still reflects typical spending. Prices are collected every month, in shops and online, and different items are given different weights based on surveys of household spending. That matters because households spend far more on some things, such as housing, food, or transport, than on others. For example, if an item takes 10% of household spending and its price rises by 10%, it adds about 1 percentage point to inflation; the same 10% rise in an item that takes 1% of spending adds only about 0.1 points.

The weighted price changes are combined into a single index number. The index is set to 100 in a base year (2015 for CPI), so a CPI of 123 means the basket costs, on average, 23% more than in the base year.

If the CPI rises from 120 to 123 over a year, the inflation rate is:

For Edexcel, the key policy anchor is that the Bank of England targets 2% CPI inflation. That means policymakers usually want low, stable inflation, not zero inflation. A small positive rate leaves a buffer against deflation, which can lead consumers to delay spending and raises the real burden of debts. You may also see CPIH and RPI in UK data. CPIH includes owner-occupiers' housing costs and council tax, while RPI is an older measure that often gives a different figure because it uses a different method and includes some housing-related costs such as mortgage interest payments. RPI is usually higher than CPI, largely because of its formula, and it lost its status as a National Statistic in 2013. It is still used for some older contracts, index-linked government bonds and student loan interest.

The three measures are similar, but they are not interchangeable:

Limits of Inflation Data

CPI is useful, but it is still only an average measure. Different households can face very different inflation rates depending on what they buy. Pensioners, for example, may spend a larger share of income on fuel and food, while younger households may be more affected by rent and transport costs.

Another problem is substitution. If the price of one item rises sharply, consumers may switch to a cheaper alternative. A fixed basket cannot fully capture that change straight away. Quality changes can also make measurement harder, because a more expensive product may partly reflect an improvement rather than pure inflation. New products and changing tastes only enter the basket when it is updated, so the index can lag behind what people actually buy. And CPI leaves out owner-occupiers' housing costs and council tax, which are a large part of many households' spending.

The big exam point is that CPI is useful, but not perfect. It gives a national headline figure, yet no single figure can describe every household's experience exactly. The same warning applies to CPIH and RPI as well: changing the treatment of housing costs or the calculation method can change the figure, but no single inflation measure captures every household's true cost of living.