"Cities don’t always grow. Sometimes they shrink, and sometimes they shrink drastically. Over the last 50 years, the city of Detroit has lost more than half its population. So has Cleveland. They’re not alone: Eight of the 10 largest cities in the United States in 1950, including Boston, have since lost at least 20 percent of their population. But while Boston has recouped some of that loss in recent years and made itself into the anchor of a thriving white-collar economy, the far more drastic losses of cities like Detroit or Youngstown, Ohio, or Flint, Mich.—losses of people, jobs, money, and social ties—show no signs of turning around. The housing crisis has only accelerated the process."