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A country’s level of development is often judged by its service industry.In more developed countries，the service industry plays a very important role in the nation’s economy and employs the majority of the labor force.In the United States，the service industry is by far the largest branch of the economy.It accounted for about 80％ of domestic GDP as of 2014.
The service sector includes a variety of private businesses that provide the public with a wide range of services.Service industries fall under several general categories，including financial services，travel and tourism，transportation，trade，entertainment and food services.Government also provides a large share of services，including postal delivery，the maintenance of roads and national defense.
Financial Services
The U.S.financial sector consists of various kinds of financial institutions such as commercial banks，investment banks，saving and loan associations and credit unions.People usually refer to all of these as banks.Banks play a very important role in the U.S.economy.They function as intermediaries in the flow of money，transferring funds from savers to borrowers.Banks also provide customers with basic means of exchange in the form of cash，checking accounts，and debit and credit cards.Americans today use relatively little cash.Most of the time，people use debit or credit cards to make payment.
The Federal Reserve System serves as the central bank of the United States.All commercial banks are required to keep a certain percentage of their deposits in the 12 Federal Reserve Banks，so they can borrow money from it.The Federal Reserve System decides monetary policy through measures such as issuing currency and setting interest rates.Its actions have significant impact on the activities of financial institutions as well as on financial markets such as the stock exchange.
Stock markets play a very important role in the U.S.economy.They help businesses to raise capital，and they offer investors potentially profitable ways to put their surplus funds to use through buying shares of company stock.There are a number of stock exchanges in the U.S.，the best⁃known of which is the New York Stock Exchange（NYSE）on Wall Street.Stock prices fluctuate based on companies’prospects for profitability，as influenced by factors such as company management，market trends and government policy.
Tourism and Transportation
Tourism is a major service industry in the United States.America has abundant resources for tourism;its vast national parks，natural wonders and other tourist attractions draw hundreds of millions of visitors each year.Americans like traveling on their yearly holiday.
In recent years，international travelers have become increasingly important for the U.S.tourist industry.People from Western Europe，China and other Asian countries，Latin America，Canada，and the Caribbean are visiting the U.S.in large numbers.Popular tourist destinations include major cities such as New York，Los Angeles，Washington D.C.and San Francisco;parks like the Yellowstone，Niagara Falls and the Grand Canyon;and theme parks like Disneyland and Universal Studios.For some states，such as Hawaii，Florida and California，the tourism industry has become a central pillar of their economies.
A vast network of railroads，highways and airlines provides convenient transportation for passengers as well as goods.The railroad network，which includes more than 226 thousand kilometers of track，has declined in importance since the beginning of the 20th century.The most important means of passenger transportation today is the automobile.The country has a network of more than 6.5 million kilometers of interstate highways which connects the major cities throughout the nation.Theoretically，someone can drive from Seattle on the west coast to New York on the east coast on the Interstate Highway system without running into a traffic light.In addition，the country has millions of kilometers of other roads and streets.Trucks and railroads are the major transporters of goods to markets.
Trade
The United States is the world’s leading trading country.Nonagricultural products usually make up about 90％ of exports，and agricultural products account for the remaining 10％.Machinery and transportation equipment are the leading categories of exports，accounting for more than one third of the total.Other major export goods include electrical equipment，computer products，chemicals and precision instruments.The largest import partners are China，Canada，Mexico，Japan and Germany，and the largest export destinations are Canada，Mexico，China，Japan and the United Kingdom.
The United States imports a large variety of products and services from other nations in order to concentrate its own economic capacity on producing those goods and services that Americans are best suited to make.Most of the imports are labor⁃intensive products such as textiles and clothes;other major import categories include machinery，raw materials and oil.For many years，the United States has had an unfavorable balance of trade，which has caused resentment among American labor unions.
U.S.trade with China has increased dramatically in recent years after the two countries signed a landmark trade agreement in 1999 and the U.S.Congress granted permanent normal trade relations with China in 2000.The total volume of trade between the United States and China reached＄521 billion in 2013 according to China’s Customs Statistics.