The U.S. Census Bureau estimates the country's population now to be 320,569,000,[5] The U.S. population almost quadrupled during the 20th century, from about 76 million in 1900.[192] The third most populous nation in the world, after China and India, the United States is the only major industrialized nation in which large population increases are projected.[193]
The United States has a very diverse population; 37 ancestry groups have more than one million members.[194] German Americans are the largest ethnic group (more than 50 million) - followed by Irish Americans (circa 37 million), Mexican Americans (circa 31 million) and English Americans (circa 28 million