US public debt

The national debt of the United States is the debt carried by the federal government of the United States. The public debt is measured as the value of the currently outstanding Treasury securities that have been issued by the Treasury and other federal government agencies. The terms national deficit and national surplus usually refer to the federal government budget balance from year to year, not the cumulative amount of debt. A deficit year increases the debt as more money is spent than is received by the government; a surplus year decreases the debt as more money is received than spent.

There are two components of gross national debt:

In general, government debt increases as a result of government spending, trade deficits, and unpaid credit, and decreases from tax or other receipts, both of which fluctuate during the course of a fiscal year. In practice, Treasury securities are not issued or redeemed on a day-by-day basis, and may also be issued or redeemed as part of the federal government's macroeconomic monetary management operations. The aggregate, gross amount that Treasury can borrow is limited by the United States debt ceiling.

Historically, the US public debt as a share of gross domestic product (GDP) has increased during wars and recessions, and subsequently declined. The ratio of debt to GDP may decrease as a result of a government surplus or due to growth of GDP and inflation. For example, debt held by the public as a share of GDP peaked just after World War II (113% of GDP in 1945), but then fell over the following 35 years. In recent decades, aging demographics and rising healthcare costs have led to concern about the long-term sustainability of the federal government's fiscal policies.

On November 7, 2016, debt held by the public was $14.3 trillion or about 76% of the previous 12 months of GDP.Intragovernmental holdings stood at $5.4 trillion, giving a combined total gross national debt of $19.8 trillion or about 106% of the previous 12 months of GDP. As of December 2017, $6.3 trillion or approximately 45% of the debt held by the public was owned by foreign investors, the largest of which were Japan (about $1.06 trillion) and China (about $1.18 trillion).

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