I DON'T understand this generation AT ALL. Back in my day it was sex, drugs and Rock and Roll. Rev. Falwell would be spinning in his grave if he knew all it would take for kids to stop fornicating was to invent a cell phone and put a couple of games on it like Angry Birds and Candy Crush. For the first time in history the majority of Americans aren't having sex even once a month, births to teenagers are the lowest since they started recording it in 1940. So put down your phone and shower and find a companion and Rock n Roll, preferably using a condom and a signed consensual sex agreement in triplicate, better safe than sorry.
I was in a fast food line and a guy in front of me had a wife and 4 kids, one he was holding in his arms. The bill for just a lunch was $38, and he was a big man and I know he didn't order all he could eat. Besides who needs a kid when you have a 100k combine to work the field. But I agree, the old why buy the cow argument. People don't need to get married to have sex anymore.
This phenomenon is largely due to women stressed out from working today. Although they contribute to the family finances, the result is a sexless marriage in many cases.
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.
One factor could be education. The more educated and successful a society is, the fewer children they have.
Plus a more educated populace tends to talk less about "getting rid of abortion" and the problems of woman working. Some still think it's the 1950s.
In the 1950s, women went to college to meet a husband, then they got married and she worked until she pregnant and then never had to work again and when her kids were in college started working for enjoyment with a charity. Now that men are no longer buying cows, she finds herself educated with no visable means of support other than working at a job just like a man.
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.