Lecture 2 - Measuring Income and Well-being

A central task of macroeconomics is to measure economic activity in a consistent and meaningful way. Policymakers, economists, and the public all require summary indicators to assess how an economy is performing, how living standards evolve over time, and how different countries compare.

The lecture motivates this measurement problem by asking how we can quantify the total income of a nation or of its average citizen. These measures matter because they inform fiscal and monetary policy, shape political debate, and underpin comparisons across time and space. However, the lecture also stresses from the outset that all such measures have limitations and should be interpreted carefully.

Exam insight

Gross Domestic Product, GDP, measures the total income of everyone in the economy. Equivalently, it measures total expenditure on the economy’s output of goods and services. These two perspectives are identical at the aggregate level because every transaction has both a buyer and a seller. Whenever one agent spends a pound, another agent earns a pound.

This identity is fundamental to macroeconomics and underpins national accounting. It also explains why macroeconomic models can be written either from the income side or the expenditure side without inconsistency.

Key identity

GDP is defined as the market value of all final goods and services produced within a country in a given period of time. Market prices are used to weight different goods and services, allowing heterogeneous outputs to be aggregated. If one good has twice the market price of another, it contributes twice as much to GDP.

GDP includes all items produced and sold legally in markets, including housing services. Rental housing is straightforward, while owner-occupied housing is included by imputing a rental value, effectively treating homeowners as paying rent to themselves.

GDP excludes most non-market activity, such as unpaid housework, childcare within families, and home-grown produce. Illicit production is also excluded, even if it has economic value.

Economic intuition

GDP includes only final goods and services to avoid double counting. Intermediate goods are already embodied in the prices of final goods. Counting both would overstate total production.

An important exception arises with inventory accumulation. Goods produced but not sold in the current period are treated as final goods because they represent current production that will contribute to future sales.

Exam insight

GDP measures production within a country’s borders, regardless of the nationality of the producer. Output produced in the UK counts towards UK GDP even if the firm is foreign owned. Conversely, output produced abroad by UK firms does not count towards UK GDP.

GDP is measured over a specific time period, typically a quarter or a year. This makes it a flow variable rather than a stock.

GDP on the expenditure side is given by:

This identity decomposes total income into four categories of spending.

Exam insight

Consumption typically makes up the largest share of GDP, reflecting household demand for goods and services. Investment is more volatile and tends to fluctuate strongly over the business cycle, making it a key driver of recessions and recoveries.

Housing is classified as investment because it provides a stream of future housing services. Financial transactions such as buying shares or bonds are excluded because they do not correspond to current production.

Government purchases include public consumption and public investment. Transfer payments such as pensions and benefits are excluded because they redistribute income rather than generate new output.

Net exports capture the external balance of the economy. A negative indicates that imports exceed exports, meaning domestic expenditure exceeds domestic production.

This slide presents recent nominal GDP figures for the UK. The upward trend reflects both real growth and inflation. Comparing nominal GDP across years without adjusting for prices can therefore be misleading when assessing changes in living standards.

The use of official national accounts data highlights the practical relevance of GDP measurement. Macroeconomists rely on such data to evaluate policy performance and economic shocks such as the Global Financial Crisis or the Covid pandemic.

GDP is not the only measure of national income. Gross National Product, GNP, measures the income earned by a country’s residents, regardless of where production takes place. It differs from GDP by net factor income from abroad.

For countries with large multinational sectors, such as Ireland, GDP can substantially exceed GNP because profits are repatriated abroad. Net National Product, NNP, adjusts GNP for depreciation, capturing the income available after maintaining the capital stock.

Exam insight

Nominal GDP values output at current prices. An increase in nominal GDP may reflect higher quantities, higher prices, or both.

Real GDP values output at constant prices from a chosen base year. By holding prices fixed, real GDP isolates changes in quantities and therefore provides a better measure of changes in economic activity.

In the base year, nominal GDP equals real GDP by construction.

The GDP deflator is a price index that measures the average level of prices of all goods and services included in GDP relative to the base year. It equals 100 in the base year and rises as prices increase.

The deflator removes the effect of inflation from nominal GDP, converting it into real GDP. It is therefore both a tool for deflation and an inflation measure in its own right.

Exam insight

This slide shows the historical evolution of real GDP. Over long periods, real GDP tends to grow, reflecting technological progress, capital accumulation, and population growth. However, growth is uneven and interrupted by business cycles.

Recessions are periods of falling real GDP. The figure highlights both the long run trend and short run fluctuations, reinforcing the distinction between growth theory and business cycle analysis.

Real GDP is often described as the best single measure of economic well-being because it captures the economy’s ability to provide goods and services. Higher real GDP allows for better healthcare, education, and material living standards.

However, it is not sufficient. GDP says nothing about how output is used, how income is distributed, or whether growth comes at the expense of environmental quality.

Real GDP per capita divides real GDP by population size to approximate average living standards. This improves comparability across countries and over time.

Despite this improvement, important dimensions of well-being remain excluded. Leisure is ignored, non-market activity is omitted, environmental degradation is not subtracted, and inequality is hidden because GDP per capita measures the average rather than the typical individual.

Median income is therefore often used as a complementary indicator, as it reflects the income of the middle of the distribution rather than the mean.

Exam insight

Mankiw, N.G. and Taylor, M.P. (2023) Macroeconomics. 6th edn. Andover: Cengage Learning.
Office for National Statistics (2025) Quarterly National Accounts, UK. London: ONS.
Office for National Statistics (2025) GDP Monthly Estimate, UK. London: ONS.