Peripherally relevant comment from the "second world"...

Important to note, I think, that rapid urbanization is often a consequence of extreme poverty and economic stagnation in the countryside, generally driven and exacerbated by a combination of terrible infrastructure, rapid population growth, and the political and economic dominance of feudal elites who often use illegal means (such as armed force) to discourage political or economic competition.

People migrate to the city because it's seen as a place with opportunities... $1 a day may seem pretty miserable, but it's more than nothing a day, and there's always that chance of hooking onto something.

Excessive focus on the cities can distract from a desperately needed focus on rural development. Can't fix one without fixing the other... if there are 2 million unemployed in Manila and you gave each one a job tomorrow, in a week there'd be 4 million more arriving for their chance.