There is a much simpler explanation: People who can will eventually move into new (or renovated) construction, because of substantial improvements in quality of

There is a much simpler explanation: People who can will eventually move into new (or renovated) construction, because of substantial improvements in quality of life. People who can't are left with the older buildings. The urban planning and architecture was often pretty good -- kindergartens, schools, shops and entertainment all nearby. In some respects, much better availability of services than some contemporary housing projects.