The definitions of inflation

Inflation refers to changes in the average prices of goods and services, affecting the economy as a whole.

Two main ways to define inflation:

• Sustained rise in average prices - Inflation is the continuous increase in the average cost of goods and services over time. Prices of some items may rise faster than average, others more slowly, and a few may even decrease.
• Fall in the value of money - Inflation can also mean that a fixed sum of money, such as £20, buys fewer goods and services than before, reducing the purchasing power of money.

Positive and negative inflation

Inflation rates can vary, indicating different economic conditions.

Types of inflation rates:

• Positive inflation - Occurs when the average price of goods and services is increasing.
• Negative inflation (deflation) - Happens when the average price of goods and services is decreasing.
• Hyperinflation - Involves extremely rapid price increases, causing money to lose its value quickly.
• Disinflation - Refers to a slowdown in the rate of inflation, such as from 7% to 3%, where prices continue to rise but at a reduced pace.

Measurements of inflation: RPI and CPI

Two primary indices measure inflation in the UK: the Retail Price Index (RPI) and the Consumer Price Index (CPI). Both track price changes but differ in scope and calculation.

Key features of RPI

The RPI measures changes in the cost of a representative selection of goods and services.

Key features of CPI

The CPI is similar to the RPI but serves as the official UK inflation measure and is used for international comparisons.

Main differences between RPI and CPI

How RPI and CPI are calculated

Both indices rely on surveys to track spending and price changes, using a 'basket of goods' to represent typical household purchases.

Steps in calculating RPI

• Living Costs and Food Survey - Involves around 7,500 households to determine spending patterns and proportions (weightings), such as 25% on housing.
• Price survey - Tracks price changes for about 850 common goods and services in the 'basket of goods'.
• Applying weightings - Price changes are multiplied by weightings and converted to an index number. The percentage change in this number indicates inflation (e.g., from 100 to 103 means 3% inflation).
• Updating the basket - Items in the basket evolve with changing technology, habits, and tastes to reflect average household spending.

Examples of changes to the basket of goods

• Items added - Daily disposable contact lenses, ebooks, blueberries, honey.
• Items removed - Local newspapers, disposable cameras, analogue radios, boiled sweets.

Calculation of CPI

The CPI follows a similar process to RPI but excludes certain items, uses a different formula, and draws from a larger population sample.

Formula for inflation rate from index numbers

$\text{Inflation rate (\%)}=\frac{\text{new index number}-\text{old index number}}{\text{old index number}}\times 100$

Where:

• New index number = Current value of the index
• Old index number = Previous value of the index

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Worked example - Calculating inflation rate from index numbers

The RPI index number rises from 105 to 108 over a year. Calculate the inflation rate.

Step 1: Identify the values

• Old index number = 105
• New index number = 108

Step 2: Apply the formula

$\text{Inflation rate (\%)}=\frac{108-105}{105}\times 100$

Step 3: Perform the calculation

$\text{Inflation rate (\%)}=\frac{3}{105}\times 100=2.86\%$

Limitations of RPI and CPI

While useful, RPI and CPI have drawbacks that can affect their accuracy.

Key limitations:

• Population coverage - RPI excludes high-income households (top 5%), while CPI omits mortgage interest payments and council tax, limiting its representation of all costs.
• Survey accuracy - Household responses in the Living Costs and Food Survey may be unreliable.
• Basket updates - The basket of goods is only revised annually, potentially missing short-term shifts in spending patterns.

The importance of RPI and CPI for government policy

RPI and CPI influence economic decisions, particularly in wages, benefits, and international trade.

Uses in wages and benefits

• Wage negotiations - Employers and trade unions use the indices as a baseline for discussions on pay increases.
• State benefits - The government applies them to adjust pensions and welfare payments.
• Index-linking - Some benefits automatically increase each year by the percentage change in the chosen index.

Role in international competitiveness

• Price competitiveness - If UK CPI inflation exceeds that of trading partners, UK goods become more expensive abroad, reducing exports and increasing imports.
• Trade impact - Higher domestic inflation makes imports cheaper relative to UK products, potentially harming the balance of trade.