2.4.2 - Injections and withdrawals

Revisiting the Circular Flow

In the simplest circular flow model, households spend all of their income on goods and services produced by domestic firms. Firms then pay that revenue back to households as factor incomes such as wages, rent, interest, and profit. Money moves round in a closed loop.

That simple version is useful as a starting point, but it is unrealistic. In practice, households do not spend all income on domestic output, and firms do not rely only on household consumption for revenue. Once we allow for money leaving and entering the flow, we can analyse changes in the level of economic activity much more clearly.

Withdrawals: Money Leaving the Flow

Withdrawals are also called leakages. They are flows of money out of the circular flow of income because that income is not being passed on as spending on domestically produced goods and services.

There are three main withdrawals.

Savings (S) are a withdrawal because households may put part of their income into bank accounts, pension funds, or other financial assets instead of spending it now. That money is not destroyed, but it does leak out of current spending on firms' output. Banks may lend savings on to firms, but the money only re-enters the flow when it is spent, for example on new machinery, and that spending is counted as investment, a separate injection.

Taxation (T) is a withdrawal because income paid to the government is taken out of private-sector spending. Income tax, VAT, corporation tax, and National Insurance all reduce the amount of income that households or firms can spend elsewhere.

Imports (M) are a withdrawal because spending goes to foreign producers rather than domestic firms. If a UK household buys an imported laptop or pays for a holiday abroad, that spending does not become revenue for UK producers.

This helps explain why the rise in UK household saving during the 2020 lockdowns weakened current spending. With many shops, restaurants and travel closed, and many households saving as a precaution, more income was being held back rather than circulating immediately through shops, firms, and workers.

Injections: Money Entering the Flow

Injections are flows of money into the circular flow of income. They add spending that does not come from the basic flow of household consumption of domestic output.

There are three main injections.

Investment (I) is spending by firms on capital goods such as machinery, equipment, factories, or vehicles. In this context, investment means adding to productive capacity, not buying financial assets. Buying shares from another shareholder only changes who owns an existing asset, so no new spending on output enters the flow. Investment is new spending entering the flow from businesses.

Government spending (G) injects money when the state buys goods and services or pays public-sector workers. Spending on school buildings, roads, or NHS equipment adds directly to demand for domestic output. Transfer payments such as state pensions and benefits are not counted in G, because the government is not buying output with them.