is there meaning to the ranking? wouldn't how big a city be be a function of its area? how big before it isnt a city anymore? is manila a city? chongqing? is

is there meaning to the ranking? wouldn't how big a city be be a function of its area? how big before it isnt a city anymore? is manila a city? chongqing? is thu duc really a separate city from ho chi minh? where does bangkok end and nonthaburi start?