AP Syllabus focus: ‘Interest on accumulated debt increases the national debt and limits the funds available for alternative government uses.’
Interest costs are a key reason national debt can become burdensome over time. This page explains how debt service grows, why it can constrain government choices, and what “burden” means in macro terms.
The basic idea: debt service compounds the problem
When the government carries outstanding national debt, it typically must make ongoing interest payments to bondholders. Those payments create a burden because they:
Add to future debt when financed by additional borrowing
Absorb budgetary resources that could have funded other public priorities
Persist even if current government spending programs are reduced
Key term: interest payments (debt service)
Interest payments (debt service): Government payments to holders of government bonds for the use of borrowed funds; typically made regularly and funded from tax revenue or new borrowing.
Interest payments are not optional in the way many discretionary programs are; failing to pay risks default, which can raise future borrowing costs and damage credibility.
How interest payments increase the national debt
If the government runs a deficit, it issues new bonds. Even if the government stops expanding program spending, the existing stock of debt still requires interest payments. If those interest payments are not fully covered by taxes, the government borrows to pay them, increasing the debt stock.
A compact way to track debt growth
This excerpt from an IMF working paper presents the standard debt dynamics equation, showing how last period’s debt rolls forward with interest via the term and then adds the primary deficit. It provides a formal, model-based justification for why interest costs can raise debt even if new program spending is restrained. Source
= National debt next period (dollars)
= National debt this period (dollars)
= Government deficit excluding interest (dollars)
= Interest owed on existing debt (dollars)
This relationship highlights the mechanical burden: even with a primary balance near zero, positive interest costs can still push debt upward.
Why interest payments limit alternative government uses
Interest payments compete with other parts of the budget.
This figure breaks total federal outlays into mandatory spending, discretionary spending, and net interest, making the budget tradeoff visible at a glance. It highlights that as net interest grows, it mechanically takes up a larger slice of total spending, leaving less room for other categories without higher taxes or more borrowing. Source
Because total revenue is limited at any point in time, higher interest costs can force policymakers toward one (or more) of the following:
Reduce other spending (infrastructure, education, research, public safety)
Raise taxes (which can be politically difficult and may change incentives)
Borrow more (which can further increase future interest payments)
The opportunity cost of debt service
In macroeconomics, “burden” often means opportunity cost: resources devoted to debt service cannot be used elsewhere. Unlike many government purchases that directly provide services, interest payments primarily transfer income to bondholders, which may not align with current policy goals.
When the burden tends to grow faster
The pressure from interest payments becomes more severe when:
The interest rate on government borrowing rises (new debt is issued at higher rates, and maturing debt is refinanced more expensively)
The debt level is large, so even moderate interest rates imply large dollar payments
Revenue growth is weak, making it harder for taxes to cover debt service without cuts elsewhere
Budget inflexibility
As interest payments take a larger share of the budget, fiscal policy can become less flexible:
Responding to recessions or emergencies may require even more borrowing
Political conflict may intensify because fewer dollars remain for noninterest priorities
Long-term planning is harder when a growing share of spending is precommitted to debt service
What “burden” does and does not mean
The burden is not simply “debt exists.” The burden arises from the ongoing requirement to devote future resources to servicing past borrowing. In practical terms for AP Macroeconomics, focus on two linked effects emphasized by the syllabus:
Interest on accumulated debt increases the national debt when financed through additional borrowing.
Interest payments limit funds available for alternative government uses by diverting budget resources away from current programs and priorities.
FAQ
No. They can be funded by higher taxes, lower noninterest spending, or new borrowing; the burden is the trade-off each option creates.
Maturing bonds must be refinanced at higher rates, and new deficits are financed more expensively, so total debt service can jump even if spending is unchanged.
Bondholders (households, firms, banks, pension funds, foreigners). Distribution matters because payments are transfers that may not match current policy priorities.
Yes, by lengthening maturities, improving fiscal credibility to reduce risk premia, and maintaining stable financing conditions—though none eliminate the obligation to pay.
Analysts look at interest payments relative to tax revenue or GDP, since affordability depends on the economy’s size and the government’s capacity to raise revenue.
Practice Questions
(2 marks) Explain one reason why interest payments can increase the national debt.
States that interest must be paid on outstanding debt (1).
Explains that if not covered by tax revenue, the government borrows to pay interest, adding to debt (1).
(5 marks) Using the idea of opportunity cost, analyse how rising interest payments on the national debt can create a burden for the government.
Defines interest payments/debt service as payments to bondholders (1).
Explains that higher interest payments absorb a larger share of the budget/revenue (1).
Applies opportunity cost: fewer funds for alternative government uses (e.g., infrastructure, education) (1).
Explains a policy response (raise taxes, cut spending, or borrow more) (1).
Links borrowing more to higher future interest costs and potentially higher debt (1).
