Cities and Urbanization Global IssueMore than half of the world’s population lives in cities, and one in eight urbanites reside in one of the 33 “megacities” (those with more than 10 million inhabitants). While urbanization creates many challenges that threaten the quality of life, it also represents our best hope of solving these challenges; that’s because the density of cities enables innovation, by readily providing testbeds to gauge the effectiveness of related solutions.