8 issues that will define cities in the 2020s

By their nature, cities are dynamic and ever-changing, shaking off the past and constantly reinventing themselves to face the future. But something seemed to happen to U.S. cities over the last decade, a kind of stasis in the face of rapid change. That may seem counter-intuitive, considering just how much urban America changed, from the introduction of new technologies and startups to building booms, increased gentrification, and rising rents. But time and time again, cities were more reactive than active.