people congregated in big cities because industry needed massive amounts of manpower.......as man is replaced by robots in industry, manufacturing becomes decentralized, beer becomes micro-brewery, shopping moves away from malls..........people don't need to live in urban areas......some millennials are repopulating old urban areas, but is city population actually increasing or decreasing.......Detroit went from 1.2 million to under 800k in the last twenty years......the Los Angeles area population has grown, but has the city population grown or declined as people relocate further away where home prices are cheaper.....