National Debt

The national debt is the total outstanding amount the United States federal government has borrowed and not yet repaid. It accumulates over time: whenever the government spends more than it collects in a year, it runs a budget deficit and borrows to cover the difference by issuing Treasury securities, and the sum of all past borrowing, plus interest, is the national debt. The single most common confusion is between the debt and the deficit. The deficit is a flow, a one-year gap between spending and revenue. The debt is a stock, the accumulated result of many years of those gaps. A deficit adds to the debt; a surplus would pay some of it down.

Because the debt and the deficit are so often conflated, it helps to keep the arithmetic straight. If the government spends $6 trillion in a year and collects $5 trillion, the deficit for that year is $1 trillion, and the debt rises by roughly that amount. A run of deficits steadily increases the debt; a rare surplus reduces it. So "the deficit fell" and "the debt fell" are different claims: the debt can keep growing even as the annual deficit shrinks, as long as the government is still spending more than it takes in.

The national debt is usually divided into two parts. Debt held by the public is the portion owed to outside investors, individuals, pension funds, banks, foreign governments and central banks, and the Federal Reserve, who hold Treasury securities. This is the part most economists watch, because it represents money the government must raise from markets. Intragovernmental holdings are amounts one part of the federal government owes another, most famously the special Treasury securities held by the Social Security and Medicare trust funds, which have taken in more than they paid out and lent the surplus to the Treasury. Adding the two gives the gross national debt; debt held by the public is the narrower and more economically meaningful figure.

Analysts often express the debt relative to the size of the economy, as a ratio of debt to gross domestic product, because a given dollar amount means something different for a large economy than a small one. That ratio, rather than the raw dollar total, is the standard way to compare debt across time and across countries. The debt also carries interest, and as it grows, so does the annual cost of servicing it, which itself becomes a large line in the federal budget and interacts with fiscal policy choices.

A separate mechanism, the statutory borrowing cap known as the debt ceiling, limits how much the Treasury may borrow and periodically forces a political confrontation; that cap is covered on its own page. Because the exact debt changes every day as securities are issued and redeemed, the Treasury publishes the current figure daily as the "Debt to the Penny" at fiscaldata.treasury.gov, which is the authoritative source for the live number rather than any figure quoted in passing.

The government finances a deficit by having the Treasury sell securities, bills, notes and bonds, to investors and to its own trust funds. Those securities are the debt. As long as the government runs deficits, it issues more securities than it retires, and the outstanding total climbs.

A hypothetical shows the stock-versus-flow relationship. Suppose a country starts a year owing $30 trillion. During the year it spends $6 trillion and collects $5 trillion, a deficit of $1 trillion, which it borrows. By year end the debt is about $31 trillion. The next year it narrows the deficit to $700 billion, which many would report as good news, but because it is still spending more than it collects, it borrows again and the debt rises to roughly $31.7 trillion. The deficit fell while the debt grew, which is exactly the distinction that gets lost in casual discussion. Only a year with a surplus, revenue exceeding spending, would actually reduce the debt.

Why governments borrow at all

• Borrowing lets a government fund investment, respond to recessions, and cover emergencies without raising taxes sharply in a single year.
• Treasury securities are widely held as a safe asset and are central to the financial system.

The concerns a large debt raises

• Rising debt means rising interest costs, which crowd out other spending in the budget.
• A high debt-to-GDP ratio can constrain a government's flexibility in the next crisis.
• The debt is only reduced by running surpluses, which are politically difficult, so it tends to grow over time.