3.2.2.1 - The circular flow of income

One flow, three measures

National income measures the flow of income generated by production over a period, usually a year. It is a flow, unlike the stock of wealth held at a date. In the basic model, households own factors of production and supply labour, land, capital and enterprise to firms. Firms produce goods and services and pay wages, rent, interest and profit. Households use income to buy output, so one person's spending becomes another person's income.

The real flows and money flows run in opposite directions: labour services move from households to firms while wage payments move back; goods move from firms to households while consumption expenditure moves back. A firm can also pay profits to its owners rather than distribute every receipt as wages.

Three approaches describe the same production:

In a simplified economy, a bakery sells bread for £100 after buying £40 of flour. Its value added is £60; the flour producer's value added is £40 if it buys no intermediate inputs. Total final output is £100, not £140. The £100 also generates £100 of factor income across the two firms and is bought with £100 of final expenditure.

This is an accounting identity, not a claim that recording income automatically causes more output. Actual expenditure includes changes in inventories: unsold output can count as investment in stocks. Planned expenditure can therefore differ from production even while measured income, output and expenditure agree. Detailed national-account adjustments are beyond this lesson's required scope; the distinction between an identity and a behavioural explanation is essential.

Nominal and real income

Nominal income is measured at current prices; real income removes price changes so that changes in purchasing power or output volumes can be compared. A rise in nominal national income could reflect higher prices, more output, or both. Use a price index covering the relevant output, with its base year equal to 100.

In an illustrative economy, nominal income is £550 billion in Year 2 and the output price index is 110, with Year 1 = 100. Real income is $550/110\times100=£500$ billion at Year 1 prices. If Year 1 nominal income was also £500 billion, output volume has not increased: all the nominal increase reflects prices. Dividing by 1.10 is the equivalent method.

A higher real national income can indicate more goods and services available, employment opportunities and tax capacity. It does not establish that every person is better off. Population growth can reduce real income per person even when the total rises; unequal distribution can leave some incomes falling. Unpaid work, leisure, environmental damage and quality of public services also matter. Compare like definitions and base prices, then ask what the measure leaves out.