<Tr> <Td_colspan="2"> Main data source: CIA World Fact Book All values, unless otherwise stated, are in US dollars . </Td> </Tr> <P> The economy of the United States is a highly developed mixed economy . It is the world's largest economy by nominal GDP and second largest by purchasing power parity (PPP). The U.S. GDP was estimated to be $19.3 trillion in 2017 It has the world's seventh - highest per capita GDP (nominal) and eleventh - highest per capita GDP (PPP) in 2016 . The U.S. dollar is the currency most used in international transactions and is the world's foremost reserve currency, backed by its science and technology, its military, the full faith of the US government to reimburse its debts, its central role in a range of international institutions since World War II and the petrodollar system . Several countries use it as their official currency, and in many others it is the de facto currency . Its largest trading partners are China, Canada, Mexico, Japan, Germany, South Korea, United Kingdom, France, India and Taiwan . </P> <P> The US economy is fueled by abundant natural resources, a well - developed infrastructure, and high productivity . It has second highest total estimated value of natural resources, valued at $45 trillion in 2016 . Americans have the highest average household and employee income among OECD nations, and in 2010 had the fourth highest median household income, down from second highest in 2007 . It has been the world's largest national economy (not including colonial empires) since at least the 1890s . The U.S. is the world's third largest producer of oil and natural gas . In 2016, it was the largest trading nation in the world as well as the world's second largest manufacturer, representing a fifth of the global manufacturing output . The US also has not only the largest economy, but also the largest Industrial sector, at 2005 prices according to the UNCTAD . The US not only has the largest internal market for goods, but also dominates the trade in services . US total trade amounted to $4.92 trillion in 2016 . Of the world's 500 largest companies, 134 are headquartered in the US . </P> <P> The United States has one of the world's largest and most influential financial markets . The New York Stock Exchange is by far the world's largest stock exchange by market capitalization . Foreign investments made in the US total almost $2.4 trillion, while American investments in foreign countries total over $3.3 trillion . The economy of the U.S. leads in international ranking on venture capital and Global Research and Development funding . Consumer spending comprises 71% of the US economy in 2013 . The United States has the largest consumer market in the world, with a household final consumption expenditure five times larger than Japan's . The labor market has attracted immigrants from all over the world and its net migration rate is among the highest in the world . The U.S. is one of the top - performing economies in studies such as the Ease of Doing Business Index, the Global Competitiveness Report, and others . </P>

When did the united states become the world's largest economy