As far as economic influence goes, I have seen evidence that in the U.S. the abortion rate tends to decline whenever the economy is strong for extended periods.
That would make sense. People will be more willing to have kids if their finances are in good shape.
Not the only factor involved, though. Germany has both lower birth rates
and lower abortion rates than Britain and France - but I doubt there's all that much of a difference in overall sex had. The difference would presumably be due to wider use of contraceptives.
