First of all,not every country has the same "population problem" so the answer to the one child question would depend on the country in question. In Europe the population rate is at a negative growth rate and in the U.S and Canada the birth rate is mildly steady. Enforcing a one child rule in a stable country will not solve overpopulation in the third world,where overpopulation is rampant. Also in places like the middle east, Latin America, Africa and India, large families are a cultural choice.....How would that be enforced without colonization? Very tricky question and quite the slippery slope. Also note that although China's population is improving, the male/female ratio is extremely unbalanced due to high rates of abortion and infanticide of the female gender. As a result China is having some pretty serious issues finding wives for the next generation.