In China it works, apparently pretty well. Chinese traditions and cultural ideals make it easier to put the good of the group ahead of individual desires. A woman who gets pregnant without permission is pressured by her sisters to have an abortion. Westerners react with horror to this, but such coercion in the East should be compared to forcing a Westerner to pick up the litter he or she has dropped on the ground in a public park. The answer, in a word is shame.
Shame is an effective control, provided the number in the group is small.
Those numbers play a role in shaping human behavior we know from experiences of the Hutterites on our own continent. When the number goes beyond 150, noncooperators destroy social unity. Hutterites respond to this threat by constant, amoebalike fissioning of their communities, thus minimizing the numbers involved in decisions. The combined experiences of the Chinese and the Hutterites tell us that a voluntary system of population control, when it is not backed by legal sanctions, can work only with small groups of people who are intimately involved with one another daily. Essentially zero, at present.