What you'll learn

• How the budget/fiscal deficit is different from the national public sector debt.
• Why deficits can be structural, cyclical, discretionary or caused by automatic stabilisers.
• Why high debt can worry governments, investors and taxpayers.
• How to evaluate whether tightening fiscal policy in a downturn is sensible.

1. The big picture: why debt control matters

Governments need to spend on health, education, defence, welfare, infrastructure and debt interest. They raise money mainly through taxation. If spending is greater than revenue, the government must borrow.

Debt control is a macroeconomic objective because very high debt may limit future policy choices. However, debt is not automatically “bad”: borrowing to fund productive investment, or to support demand in a recession, may improve long-run living standards.

The key measurement idea is that a deficit is a flow each year, while debt is a stock built up over time.

2. Measuring the deficit and the debt

A budget deficit, also called a fiscal deficit, occurs when government spending is greater than government revenue in a given year.

A simple budget balance can be written as:

$$B=T-G$$

where $B$ is the budget balance, $T$ is tax revenue and other government receipts, and $G$ is government spending. If $B<0$, there is a deficit. If $B>0$, there is a surplus.

The debt-to-GDP ratio compares public sector debt with the size of the economy:

$$Debt-to-GDP\; ratio=\frac{public\; sector\; debt}{nominal\; GDP}\times 100$$

Nominal GDP means the money value of national output at current prices.

3. Structural and cyclical deficits

An actual deficit is the deficit the government records in a particular year. But economists often split it into two parts.

In a downturn, unemployment rises, profits fall and consumer spending weakens. This reduces income tax, corporation tax and VAT receipts. At the same time, spending on benefits may rise. That can create a larger cyclical deficit even if the government has not made any new policy announcement.

A structural deficit is more persistent. It suggests the underlying level of spending is too high relative to revenue, even after allowing for the state of the economy.

4. Why deficits happen: discretionary and automatic policy

Fiscal policy means the use of government spending, taxation and borrowing to influence the economy.

A deficit can result from discretionary fiscal policy. This means deliberate government decisions, such as cutting income tax, raising public investment, increasing defence spending, or offering emergency support. UK examples include pandemic support schemes and energy-bill support during the cost-of-living squeeze.

A deficit can also result from automatic stabilisers. These are features of tax and welfare systems that automatically reduce fluctuations in the economy without new legislation. In a recession, tax receipts fall and welfare payments rise, supporting household incomes but increasing borrowing.

5. Why governments worry about high public sector debt

Opportunity cost of interest payments

Opportunity cost is the next best alternative forgone. When the government pays interest on debt, that money cannot be used for other priorities such as the NHS, education, tax cuts or infrastructure.

Debt interest can rise if the stock of debt grows or if interest rates rise. This became more relevant after the Bank of England increased interest rates to tackle high inflation following global supply-chain shocks and the cost-of-living squeeze.

Credit downgrades and refinancing confidence

A credit rating is an assessment by ratings agencies of how risky a borrower is. A credit downgrade means the borrower is judged to be riskier. For a government, this can increase the yield investors demand on government bonds.

In the UK, government bonds are called gilts. Refinancing means replacing maturing debt with new borrowing. If investors lose confidence in the government’s fiscal plans, they may demand higher yields to buy gilts. This can make future borrowing more expensive.

However, the UK borrows in its own currency and has deep financial markets, so default risk is usually much lower than for countries borrowing heavily in foreign currency.

Crowding out and slower growth

Crowding out occurs when government borrowing reduces private sector activity. This may happen if heavy borrowing pushes up interest rates, making it more expensive for firms to invest. It may also happen if the government absorbs scarce labour, land or materials that private firms would otherwise use.

But crowding out is not automatic. A Keynesian economist would argue that during a recession, when there is spare capacity and weak private investment, government borrowing may “crowd in” private sector activity by increasing aggregate demand and confidence.

6. Should governments tighten fiscal policy in a downturn?

Fiscal tightening, also called contractionary fiscal policy or austerity, means reducing the deficit through spending cuts, tax rises, or both.

The argument for tightening is that it may reduce the structural deficit, reassure investors, lower the risk of credit downgrades and reduce future debt-interest costs. This can be important if markets doubt whether the government has a credible plan to manage debt.

The argument against tightening is that a downturn is exactly when private consumption and investment are already weak. Higher taxes or lower government spending reduce aggregate demand, which may reduce real GDP and raise unemployment.

The diagram shows that if the economy is already below potential output, fiscal tightening can shift AD left from AD1 to AD2. Real GDP falls from Y1 to Y2, and the recessionary output gap widens. Lower output can also reduce tax receipts and increase welfare spending, partly offsetting the intended deficit reduction.

A balanced evaluation is usually strongest. Fiscal tightening may be more appropriate when inflation is high, the economy is near full capacity, the structural deficit is large, or market confidence is fragile. It may be less appropriate when unemployment is high, the multiplier is large, interest rates are low, and public investment could raise long-run productive capacity.

7. Is debt always a bad thing?

No. Debt can be sustainable if the economy grows fast enough relative to the interest cost of borrowing. It can also be justified if borrowing finances investment that increases future tax revenues, such as transport, skills, energy infrastructure or digital networks.

The important distinction is between borrowing for short-term current spending and borrowing for projects that improve the economy’s supply-side performance. Even then, governments must consider waste, delays and government failure.