At 3.79 million square miles (9.83 million km2) and with over 309 million people,the United States is the third or fourth largest country by total area,and the third largest both by land area and population.It is one of the world's most ethnically diverse and multicultural nations,the product of large-scale immigration from many countries.The U.S.economy is the world's largest national economy,with an estimated 2009 GDP of $14.3 trillion (a quarter of nominal global GDP and a fifth of global GDP at purchasing power parity).
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