Commentary

摘要

For the first time, more people are living in cities than rural areas. According to the 2010 U.S. Census, nearly 81 percent of the U.S. population lives in cities. The U.N. Department of Economic and Social Affairs (DESA) reports that 54 percent of the worldwide population lives in cities, and that number will reach 66 percent by 2050. The latest DESA report states that 10 megacities-cities with 10 million people or more-existed in 1990 and were home to slightly less than 7 percent of the global urban population. Today, 28 megacities exist worldwide and are home to some 453 million people, or about 12 percent of the world's urban population. Population projections released in January by the U.S. Conference of Mayors state that by 2042, three new megacities will join the existing four in the U.S. In addition, the organization predicts the number of major U.S. metropolitan areas-those with more than 1 million people-will rise from 51 in 2012 to 70 in 2042.