At least, based on this graphic:
With the exception of the city-states (Monaco, Hong Kong), it is rather clear that population density in the selected countries can be extreme in urban areas.
One needs then to ask the reasons for such rapid and massive urbanization (which leads to Mike Davis’s Planet of Slums) as well as its consequences. How do cities cope, in term of infrastructure and urban development, with such increase in their population and such high densities? Often, not very well and one can see the ecological nightmares in shanty towns and other poverty-inflicted areas.
The question of the global urban poor is an essential one for development policies.