Chapter 43: The US Deficit and National Debt

Book: Economics 101

Author: Alfred Mill & Michele Cagan

Type: Chapter

Category: Economics

Difficulty: Beginner

Reading time: 7 min

Core idea

Deficit and debt are different things, and conflating them produces most of the bad fiscal-policy talk in circulation. The budget deficit is a flow: the gap between what the government spent and what it took in during a single year. The national debt is a stock: the cumulative total of every past deficit, minus any past surpluses, that has not yet been paid back. The US Treasury closes annual deficits by issuing bonds — Treasury bills (≤1 year), notes (2–10 years), and bonds (20–30 years) — and pays bondholders interest until maturity, then returns the principal in a lump sum. Two of the headline numbers worth memorising: the US federal deficit was about $1.7 trillion in FY2023, and the national debt sat near $33.2 trillion, roughly 123% of GDP. Interest payments alone now exceed $395 billion a year and are one of the federal government’s largest line items.

Author’s argument: Deficits and debt are not signs of weakness on their own — every modern government runs them. What matters is the trajectory, the use to which borrowing is put, and whether interest can be serviced indefinitely without crowding out everything else.

Why it matters

Deficit-vs-debt is the most common confusion in fiscal talk

When a politician says “we cut the deficit by $300 billion,” that does not mean the debt fell — the debt still grew, just by less. When a commentator says “the debt is up another trillion,” they usually mean cumulative new borrowing across multiple deficits. Getting the flow-vs-stock distinction right is the first step to following any serious fiscal discussion.

Debt-to-GDP, not raw dollars, is the right denominator

“$33 trillion” is unfathomable. 123% of GDP is interpretable: it means the country owes slightly more than one year’s economic output. By that yardstick, the US is heavily indebted but nowhere near outliers like Japan (~256%). Debt-to-GDP also explains why growing the economy can shrink the debt burden even when the dollar amount of debt rises — the denominator grows faster than the numerator.

Interest is the lever that turns sustainable debt into a problem

A 1% rise in average interest cost on $33 trillion adds $330 billion in annual interest expense — more than the entire federal education budget. When rates rise, the cost of servicing existing debt rises with each new bond auction. Service cost is the crowding-out mechanism that fiscal hawks worry about most.

Key takeaways

Key takeaways

• Deficit = annual gap between government spending and revenue (a flow). Debt = cumulative unpaid borrowing across all past deficits (a stock).
• FY2023: US spending $6.13T, revenue $4.44T, deficit $1.7T. US national debt ~$33.2T (October 2023), ~123% of GDP.
• The Treasury closes deficits by issuing three kinds of bonds: T-bills (≤1 yr), T-notes (2–10 yr), T-bonds (20–30 yr). All pay periodic interest and return principal at maturity.
• Two ways to shrink a deficit: raise revenue (taxes, audits, growth) or cut spending. Both have political and economic costs.
• Recessions automatically widen deficits — tax revenue falls and safety-net spending rises. Booms automatically narrow them.
• Debt-to-GDP ratio is the right measure for international and historical comparisons. Japan is highest (~256%); the US sits at ~123%.
• About 20% of US debt is held by other arms of the US government (the Fed alone holds ~$5T). The rest is held by domestic investors and foreign governments — Japan and China are the largest foreign holders.
• 'Full faith and credit' is the unconditional guarantee that the US will honour all interest and principal payments. It is why Treasury debt is treated as the global benchmark for risk-free yield.

Mental model — deficits accumulate into debt; debt is serviced by more borrowing

click to zoom

Read it as: revenue and spending meet at the annual scale. Surpluses (rare) can pay debt down; deficits (the norm) get financed by issuing new Treasury bonds, which add to the cumulative debt stock. The debt then generates interest payments that are themselves a spending line — creating the feedback loop that fiscal hawks worry about.

Mental model — three kinds of Treasury debt

click to zoom

Read it as: the Treasury issues three maturities to suit different investor preferences. About a fifth of the resulting debt is held internally by other US government arms (especially the Fed). The rest is held by domestic savers (directly or via funds) and by foreign governments — Japan and China are the two largest foreign creditors.

Practical application

Reading any debt or deficit headline

A four-step decoder

1. Is it a deficit number or a debt number? Deficit = this year’s gap. Debt = the running total. They have different units (deficit is $/yr, debt is $).
2. Compare to GDP, not to itself. “$1.7T deficit” sounds huge; ~6.5% of GDP is the more useful frame. “$33T debt” sounds catastrophic; 123% of GDP is interpretable.
3. Check the trajectory, not the level. Is debt-to-GDP rising, falling, or flat? Rising in a recession is normal; rising in a boom is alarming.
4. Look at the cost of service. If interest is consuming more than ~10% of federal outlays, the math gets harder. The US is in that zone now.

How deficits respond to the economy

1. Recessions widen deficits automatically. Tax revenue drops (lower wages, lower profits, fewer transactions) at the same time as safety-net spending rises (unemployment, food assistance). These are called automatic stabilisers.

2. Booms narrow deficits automatically. Tax receipts climb; safety-net spending falls. The 2001 surplus came at the end of a long expansion.

3. Discretionary policy choices can amplify or counter the automatic effects. A tax cut in a boom widens the deficit further; stimulus in a recession does too. Whether that’s good policy depends on which school of macroeconomics you ask (see chapter 40).

4. Wars and crises break both directions. Civil War debt: $65M → $2.7B in five years. WWI: to $27B. WWII: to $260B. COVID-19: trillions in new debt across 2020–2021.

Example: a household analogy that mostly works

Imagine a household earning $70,000 a year that spends $80,000 a year. The $10,000 gap is the household’s annual deficit. They put it on a credit card. After a decade of that, they owe $100,000 in cumulative credit-card debt — their debt. Servicing that debt at 20% interest costs $20,000 a year, which is now part of next year’s spending.

Now stretch the analogy carefully:

• The US can issue its own currency — a household can’t. This loosens but doesn’t eliminate budget constraints; printing money to pay debt risks inflation.
• The US borrows at low rates because Treasury debt is the world’s benchmark risk-free asset, backed by the full faith and credit of the US government. A household borrows at credit-card rates.
• The US has a perpetual existence. It rolls maturing debt into new debt forever; a household eventually retires or dies.
• The right denominator for a household is income; for a government, GDP — the productive capacity that ultimately backs the debt.

The analogy is useful for grasping the flow-vs-stock distinction and the compounding nature of interest. It is misleading if pushed to suggest the US has the same constraints as a household. Most professional economists’ disagreements about debt sustainability are really arguments about how far the analogy stretches.

Caveats

Caution

There is no consensus level of debt-to-GDP at which a sovereign borrower in its own currency “must” default. Japan has run >200% debt-to-GDP for years without crisis. Argentina has defaulted at much lower levels. What matters is the credibility of the borrower, the currency the debt is denominated in, and the productive use of the borrowed funds. Treat any politician’s claim that “we’ll go bankrupt at X%” as rhetoric, not arithmetic. Conversely, treat any claim that “deficits don’t matter” with equal skepticism — interest costs are real, they crowd out other priorities, and they constrain future fiscal choices.

Related lessons

Related

Chapter 38: GDP — Government Spending and Exports G as a component of GDP — the spending side of the deficit math, with the multiplier debate. Concept: Fiscal policy How tax and spending choices feed directly into deficits and debt. Concept: Interest rates Why the cost of servicing debt is the most important number to watch as debt grows. Concept: Gross domestic product The denominator that turns the headline debt number into something interpretable.