Gross domestic product
Gross domestic product (GDP) is a monetary measure of the market value of all the final goods and services produced in a period of time, often annually 
GDP (nominal) per capita does not, however, reflect differences in the cost of living and the inflation rates of the countries; therefore using a basis of GDP per capita at purchasing power parity (PPP) is arguably more useful when comparing differences in living standards between nations.
National debt of the United States
GDP is a measure of the total size and output of the economy. One measure of the debt burden is its size relative to GDP, called the "debt-to-GDP ratio." Mathematically, this is the debt divided by the GDP amount. The Congressional Budget Office includes historical budget and debt tables along with its annual "Budget and Economic Outlook." Debt held by the public as a percentage of GDP rose from 34.7% GDP in 2000 to 40.5% in 2008 and 67.7% in 2011.