Incidentally, a thing that is sometimes not realized even by people who worry about population problems is that population growth depends on when people have children, as well as on how many they have. Since populations tend to increase by a certain proportion per generation, it follows that if you space the generations out more, the population will grow at a slower rate per year. Banners that read ‘Stop at Two’ could equally well be changed to ‘Start at Thirty’! But in any case, accelerating population growth spells serious trouble.
