us economy

The economy of the United States is the
world's largest national economy. Its nominal
GDP was estimated to be over $15 trillion in
2011,approximately a quarter of nominal
global GDP.Its GDP at purchasing power
parity is the largest in the world, approximately
a fifth of global GDP at purchasing power
parity.The U.S. economy also maintains a
very high level of output. The U.S. is one of the world's wealthiest nations with per capita GDP (PPP) of $48,450,
the 6th highest in the world.The U.S. is the largest trading nation in the world. Its four largest export trading
partners are as of 2010: Canada, Mexico, China, and Japan

The economic history of the United States has its roots in European settlements in the 16th, 17th, and 18th centuries.The American colonies went from marginally successful colonial economies to a small, independent farming
economy, which in 1776 became the United States of America. In 180 years the United States grew to a huge,
integrated, industrialized economy that still makes up over a quarter of the world economy. As a result, the U.S.'s GDP per capita converged on and eventually surpassed that of the U.K., as well as other nations that it previously trailed economically. The economy has maintained high wages, attracting immigrants by the millions from all over the world.

The United States has been the world's largest national economy since at least the 1920s.
For many years following the Great Depression of the 1930s, when
danger of recession appeared most serious, the government
strengthened the economy by spending heavily itself or cutting taxes so
that consumers would spend more, and by fostering rapid growth in the
money supply, which also encouraged more spending. Ideas about the
best tools for stabilizing the economy changed substantially between
the 1930s and the 1980s. From the New Deal era that began in 1933, to
the Great Society initiatives of the 1960s, national policy makers relied
principally on fiscal policy to influence the economy. The approach,
advanced by British economist John Maynard Keynes, gave elected
officials a leading role in directing the economy, since spending and
taxes are controlled by the U.S. President and the Congress. The "Baby
Boom" saw a dramatic increase in fertility in the period 1942–1957; it was caused by delayed marriages and
childbearing during depression years, a surge in prosperity, a demand for suburban single-family homes (as opposed
to inner city apartments) and new optimism about the future. The boom crested about 1957, then slowly declined.
A period of high inflation, interest rates and unemployment after 1973 weakened confidence in fiscal policy as a tool
for regulating the overall pace of economic activity