The economy of the United States has been the world's largest since the early 1870s; its gross domestic product (GDP) was estimated as $13.8 trillion in 2007. It is a mixed economy and private firms make the majority of microeconomic decisions, while being regulated by the government. The U.S. economy maintains a high level of productivity (GDP per capita, $45,900 in 2007 with the U.S. population hitting 302 million), although it is not the world's highest. The U.S. economy has maintained a high overall GDP growth rate, a low unemployment rate, and high levels of research and capital investment. Major economic concerns in the U.S. include national debt, external debt, entitlement liabilities for retiring baby boomers who have already begun entering the Social Security system, corporate debt, mortgage debt a low savings rate, and a large current account deficit.

As of June 2007, the gross U.S. external debt was $12 trillion, (see List of countries by external debt). The most recent estimate of gross public debt (also known as national debt and refers to what is owed by the combined public sector to both domestic and foreign creditors; see List of countries by public debt and global debt) was 37% of GDP in 2007, which was lower than that of Japan, Italy, France, Germany, Canada, India, Brazil, or the United Kingdom. The national debt includes the amount of the cumulative government deficits and interest.