National Debt
The total accumulated stock of government borrowing — the sum of all past budget deficits minus surpluses, financed through outstanding bonds.
The national debt is the total outstanding stock of government liabilities — the cumulative result of all past budget deficits and surpluses. It is held by domestic and foreign investors, other government agencies (intragovernmental debt), and central banks.
Markets care about the debt-to-GDP ratio as a measure of debt sustainability. Rapidly rising debt relative to GDP can raise concerns about a government's ability to service obligations, leading to a widening sovereign credit spread and potential currency weakness. At extreme levels, it can constrain future fiscal policy response during downturns.