[s_dev]

I think perhaps you're conflating world population with the Chinese population. Overpopulation can occur in small areas without the world being too overpopulated as a whole -- most of them in SE Asia. If theres lots of people and limited resources, the math simply won't hold up. It affects issues like the environment and human health.

[eru]

Singapore is doing fine at high population density.

[sjwright]

Singapore doesn't exist in a vacuum. An enormous amount of foreign low population density agricultural land is sustaining their lifestyles.

[s_dev]

Singapore is very developed. Overpopulation is more a problem for densely populated developing places - Bangladesh, Victorian London, South American shanty towns et cetera.

[eru]

Yes. Though they only developed in the last 50 years.