Contents: 7 sections
AQA A-level Economics 7136 · specification section 3.2.1
Why this topic matters
Every macro question hands you numbers: an index, a growth rate, a GDP per capita comparison. Specification section 3.2.1 is about reading them properly, and it contains two things students routinely meet for the first time in the exam: index numbers and the limitations of national income data.
The habit worth building is simple. Before using a figure, ask what it measures, what it leaves out, and what it is being compared with.
Macroeconomic indicators
The main indicators, each covered in detail elsewhere:
- Real GDP and the growth rate ([6.1](/aqa-economics/6-1-economic-growth-and-the-cycle))
- The inflation rate, via CPI ([6.2](/aqa-economics/6-2-inflation-employment-and-the-balance-of-payments))
- Unemployment, via the Labour Force Survey and the claimant count
- The current account of the balance of payments
- Supporting measures: productivity, the budget balance, income distribution
Index numbers
An index number expresses a value relative to a chosen base year, which is set to 100.
Index = (value in year ÷ value in base year) × 100
Reading them
An index of 112 means the value is 12 per cent above the base year, not 112 per cent above.
To find the change between two non-base years, work in percentages of the earlier figure, not by subtracting the index points. From 120 to 132 is a rise of 12 index points but 10 per cent (12 ÷ 120).
That distinction is examined directly and is the most common arithmetic error in the topic.
Weighting
A price index is weighted by how much households actually spend on each item, so a 10 per cent rise in the price of housing moves CPI far more than a 10 per cent rise in the price of postage. The weights are updated periodically as spending patterns change.
Why they are used
- They make different units comparable: prices, output and wages can all be indexed and plotted together.
- They show proportional change clearly over long periods.
- They allow a basket of many items to be summarised in a single series.
Limitations
- The base year matters: an unusual base year distorts every comparison drawn from it.
- Weights become outdated between revisions, so the index tracks a basket people no longer buy.
- Quality change is hard to capture: a phone costing the same as five years ago is not the same product.
- The index gives no information about distribution: a national CPI describes nobody's personal inflation rate exactly, and low-income households facing a different basket can experience a very different rate.
Uses and limitations of national income data
The uses
- Comparing living standards over time within one country.
- Comparing countries, once the figures are made comparable.
- Assessing policy, since most macro objectives are measured against it.
- Informing business and investment decisions about where demand is growing.
Making the comparison valid
Three adjustments, and an answer that omits them loses marks:
- Real, not nominal. Nominal GDP rises with inflation alone. Use real GDP, which holds prices constant, to see whether output actually rose.
- Per capita, not total. A country whose GDP rises 2 per cent while its population rises 3 per cent has become poorer per person.
- Purchasing power parity. Converting at market exchange rates understates income in countries where non-traded goods such as housing, food and services are cheap. PPP adjusts for what money actually buys locally, and it is the right basis for comparing living standards across countries.
Limitations as a measure of welfare
- The informal and unrecorded economy is excluded, and it is far larger in some countries than others, so the same figure means different things.
- Unpaid work, including childcare and voluntary work, is not counted, even though it produces real welfare.
- Income distribution is invisible: GDP per capita is a mean, so it can rise while most people gain nothing.
- Negative externalities are not deducted. Pollution and congestion raise measured output through the spending needed to deal with them.
- Quality of life factors, leisure time, health, security, political freedom, are absent entirely.
- Public services are valued at cost of provision rather than at what they are worth, which understates their contribution.
This is why composite measures such as the Human Development Index exist, and why a good answer treats national income data as a useful but partial measure rather than as a definition of welfare.
Worked example
An economy's nominal GDP rises from $500bn to $540bn. Over the same year the GDP deflator rises from 100 to 105 and population rises by 2 per cent.
Nominal growth = (540 − 500) ÷ 500 = 8 per cent.
Real GDP in the second year = 540 × (100 ÷ 105) = $514.3bn, so real growth = (514.3 − 500) ÷ 500 = 2.9 per cent.
Real GDP per capita growth ≈ 2.9 − 2 = 0.9 per cent.
So headline growth of 8 per cent corresponds to less than 1 per cent improvement per person. Stating that gap is the point of the whole topic.
Common exam mistakes
- Reading an index of 112 as "112 per cent higher".
- Calculating the change between two non-base years by subtracting index points and calling the answer a percentage.
- Comparing nominal figures across years, or total GDP across countries of different sizes.
- Converting at market exchange rates when comparing living standards, instead of PPP.
- Listing limitations of GDP without saying which would matter most for the country in the question.
- Treating a rise in GDP per capita as proof that people are better off, when it is a mean.
Quick revision
- Index = (value ÷ base-year value) × 100; the base year is 100.
- An index of 112 is 12 per cent above the base year. Between non-base years, divide the change by the earlier figure.
- Price indices are weighted by household spending, and the weights date.
- To compare validly: real not nominal, per capita not total, PPP not market exchange rates.
- GDP omits the informal economy, unpaid work, distribution, externalities and quality of life, and values public services at cost.