There's a slight problem with this analysis. While it may have made a lot of sense back in the 50s and 60s, if you look at things now, it doesn't. Go into downtown DC, NYC, SanFran, etc., and instead of a bunch of poor brown people, you'll find a bunch of rich white people, and the housing costs are astronomical. So you'll find a bunch of younger, professional, frequently single, and usually childless white people living there for the short commute, walkability, access to nice restaurants and nightlife, etc., but then when they have kids, that 400 square foot condo or apartment just isn't livable any more so they want to move out to where they can afford some more space.
If you really want to stop this phenomenon, the problem is with government and zoning AFAIC. You need to build a lot more housing (and good-sized housing too, not less than 500sf) to greatly increase the housing supply, which will then lower prices and get people to stay in the city. Lower housing prices would also keep poorer people from having to commute so much since they certainly can't afford inner-city prices either. With modern building technology, it really shouldn't be that hard to build bigger/taller buildings and make more space for everyone, but no one really wants to do that for some reason.
If you really want to stop this phenomenon, the problem is with government and zoning AFAIC. You need to build a lot more housing (and good-sized housing too, not less than 500sf) to greatly increase the housing supply, which will then lower prices and get people to stay in the city. Lower housing prices would also keep poorer people from having to commute so much since they certainly can't afford inner-city prices either. With modern building technology, it really shouldn't be that hard to build bigger/taller buildings and make more space for everyone, but no one really wants to do that for some reason.