<P> 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 . </P> <P> 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 . </P> <P> 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; $6.2 trillion or approximately 45% of the debt held by the public was owned by foreign investors, the largest of which were Japan and China at about $1.09 trillion for Japan and $1.06 trillion for China as of December 2016 . </P> <P> The United States government has continuously had a fluctuating public debt since its formation in 1789, except for about a year during 1835--1836 . To allow comparisons over the years, public debt is often expressed as a ratio to gross domestic product (GDP). </P>

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