Good argument, maybe it should be based on the area of land controlled by each nation? Population density or Tons of CO2 produced per square mile?
The problem with per capita policy is it encourages over population which makes the problem worse.
And China actually made effort in past to control that as well (One Child policy).
Only recently they relaxed it to avoid social side effects and unbalance in proportion between generations, and fertility rate is still bellow that of the USA (1.62 vs 1.80).
