The U.S. Census Bureau currently estimates the country's population to be 321,813,000.[197] The U.S. population almost quadrupled during the 20th century, from about 76 million in 1900.[198] 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.[199] In the 1800s the average woman had 7.04 children, by the 1900s this number had decreased to 3.56.[200]
The United States has a very diverse population; 37 ancestry groups have more than one million members.[201] 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).[202][203]
White Americans are the largest racial group; Black Americans are the nation's largest racial minority (note that in the U.S. Census, Hispanic and Latino Americans are counted as an ethnic group, not a racial group), and third largest ancestry group.[201] Asian Americans are the country's second largest racial minority; the three largest Asian American ethnic groups are Chinese Americans, Filipino Americans, and Indian Americans