It strikes me that there are roughly three categories: 1) people who choose to never have kids; 2) people who want kids, but choose to wait until they can live comfortably, save for college, and so on; and 3) people who just want kids, and figure that they'll work out the details later.
Maybe it's the first and second categories who tend to end up in large cities. And maybe it's the third category who tend to live in the poorest regions. That is rather consistent with the standard understanding that education and economic development tend to reduce population growth.
Maybe it's the first and second categories who tend to end up in large cities. And maybe it's the third category who tend to live in the poorest regions. That is rather consistent with the standard understanding that education and economic development tend to reduce population growth.