Population

The United States is the third most populous nation in the world, ranking behind China and India. According to the US Census Bureau（人口普查局）, America has a population of 329 million in 2019, with an 0.7% population growth rates annually in the last decade. This adds about 2 million people every year. Most Americans are descended from immigrants. Immigration now contributes roughly a third of the annual US population increase.

     The distribution of the population in the US is rather uneven. The population density（人口密度）varies from 4 pop./km² to the higher density of 100 pop./km² or more, and the average number is about 35pop./km². The most densely populated region is the northeastern part of the country. The region takes up about one quarter of the total land area, but about half of the population is living there. The Great Plains have a comparatively small population. The South has a population of over 100 million. The West is not densely populated, except for some metro politan center like Los Angeles and San Francisco. The most populous state in the US is California, followed by Texas and Florida, but the most populous city is the city of New York, followed by Los Angles and Chicago.