One son policy
Watching 60 minutes last night on the fact that in China's new generation, there are 120 boys for every 100 women, due to the one-child-policy and the abortion of girls by those who insist on a son, an obvious answer came to me.
Instead of a one-child policy, have a one-son policy. Ie. after you have your first boy, you must stop. (China actually forces sterilization or insertion of an IUD under surveillance, which I obviously don't think is a great way to do things.)
A one-son policy, would obviously increase the population pressure, since strice one-child means 1 child for every woman (though in practice it is not perfect, so it's a bit more than that,) while one-son probably results in about 1.7 children per woman.
But in theory, there would be far less aborting of girls. There might be a cap of 3 children, which would mean that after 2 girls, the parents might consider abortion of a third, but this would apply to a much smaller fraction of pregnancies than it does today. In addition, a number of couples would stop with all girls after 2 or many times even 1, both because they can't afford more children, or state pressure still pushes them to stop. The policy would actually be that one should still have only one child, but that draconian measures would not be taken on those who have daughters who insist on trying for a son.
The key is simply to present the easiest path. Right now aborting a child based on sex is illegal, it's illegal for a doctor to tell the parents the sex of a child, and that would probably remain true. They just have to make it so that those daring enough to break the law to identify and then abort a girl would take the slightly easier, if perhaps more bureaucratic, path of having another child.
And of course, as long as you're not aborting based on sex, you will get an even sexual balance no matter what rules you place on when to stop.
They need to do something. Lots of evidence suggests that a giant surplus of men who will never find women will sharply increase the crime rate and cause other problems. (Though perhaps it will cause revolution which would probably not be all bad.) Already one new nasty crime of desperation has sprung up -- kidnapping girls, sometimes just as babies, to be future brides. I had hoped that being so valuable would increase the women's power, but this may have been a false hope.
A search reveals I am not the only one with this idea, but it has not yet gathered much of a foothold. Both approaches are draconian, of course, and have no place in a free society.