Mayors weigh in: America’s cities have been staging a comeback in recent years, with many downtown areas attracting a new wave of educated Millennials. With this influx of residents comes a demand for housing. In the latest Menino Survey of Mayors, released this week by the Boston University Initiative on Cities, a little over half (51 percent) of U.S. mayors surveyed cite housing costs as the most common reason that people move out of their city.