the level of the national debt is limited by
National debt of the United States 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.[3] The aggregate, gross amount that Treasury can borrow is limited by the United States debt ceiling.[4]