Earlier quoted context omitted.
I don't mean to have this come across as snarky, at all, but really the reference for this is the whole of human history. Wealth is basically self-concentrating. Our political systems tend to end up with a few capital (and often Capitol) cities where the spoils from the plundering, both metaphorical and literal, end up. The original article does present some interesting and relevant examples of countervailing forces…
That's not snarky, and you have a point. But even if things seem "really obvious" and we can tell "just by looking at the facts", I feel better if someone has looked at the data and shown that to be the case. We aren't living in the feudal era, and a lot of people like to think that the reason people move to the cities is because of (for instance) bars and restaurants, museums and the opera, high-paying jobs and so o…
How do you define wealth concentration, for example? If your definition is flawed, you can throw out the entire model.