National Income
Definition
National income: the total value of a country's output, income and expenditure over a given period, usually one year.
Value added: the value a firm adds to its inputs, equal to its sales revenue − the cost of bought-in goods and services; summing value added avoids double counting.
Three Ways to Measure
- The output method sums the value added at each stage of production, counting only final goods and services so that inputs are not counted twice.
- The income method sums all incomes earned by the factors of production: wages, rent, interest and profit.
- The expenditure method sums all spending on final output by households, firms, government and the rest of the world.
Key Idea
- The three methods are three views of the same circular flow of activity.
- The national income identity is output = income = expenditure, so in principle all three give an identical total.
Why They Are Equal
- To produce output, firms must hire factors of production and pay them for their contribution.
- So every £1 of output produced generates £1 of factor income (wages + rent + interest + profit).
- Households then spend that income on goods and services, so income turns into expenditure.
- The same £1 is therefore counted as output, as income and as expenditure as it flows round the economy.
Example
- A bakery bakes and sells bread worth £500 in a year, so its final output is valued at £500.
- Wages £300, rent £50, interest £50 and profit £100 total £500, and buyers spend £500, so output = income = expenditure = £500.
Why It Matters
- National income measures the total economic activity of a country over a year.
- It is the starting point for measuring economic growth and average living standards.
- It lets economists compare performance over time and between economies.
- It depends, though: a higher figure need not mean higher welfare, because it says nothing about how income is shared or about unpaid work the figures miss.
Exam technique
- State clearly that output, income and expenditure give the same total by the national income identity.
- Justify it by tracing value from production, to factor income, to spending.
Common Mistake
- National income is a flow measured over a period, not a stock held at a point in time.
- Do not confuse it with a country's accumulated wealth, and count only final output to avoid double counting.
Self review
- Define national income.
- Name the three methods of measuring it.
- Why do the three methods give the same total?
- Is national income a flow or a stock?
