In many ways they are experiencing an acceleration of already deep-seated trends. The percentage of Americans living in suburbs rose from 13 percent of the metropolitan population in 1940 to 86 percent in 2017, a gradual increase of 2 percent a year. And since 2012, suburbs and exurbs have accounted for about 90 percent of all metropolitan growth. This dispersion has occurred not only in the United States but in the old cities of Europe, too, including London and Paris.