
One factor could be education. The more educated and successful a society is, the fewer children they have.
Actually there's a body of research that abortion decreased crime (see http://freakonomics.com/2005/05/15/abortion-and-crime-who-should-you-believe/ for some links and arguments on both sides). Would be interested to see the body of work that makes you think it hurt the economy, or is that just your personal opinion based on a strong hunch? There is a direct inverse correlation between wealth of a country and birth rate across all of the 195 countries in the world that pretty much makes an argument for increased birthrates as a driver of economic growth a little silly. That's not to say falling birth rates aren't a problem across the developed world. But its a problem that's easily solved by increasing immigration from the developing world into the countries with low birth rates.If they ever get rid of abortion, then birthrate will change for the better, termination of babies has been 2.5 generations, millions of kids that turn economy into super drive we lost.