I think you are making a few assumptions that aren't guaranteed. I don't think 9% return is a given or that we will make up for it because we are behind. You are assuming that our economy is, structurally, very similar to the past. I don't think that is really the case.
The biggest shift is obviously in the transition from manufacturing to the service sector as well as the huge increase of credit use around that time as well. I think this had pretty serious consequences because it was the beginning of huge inequality and the decline of the middle class. All of that resulted in stagnant wages and depressed demand because everyone's money is now going towards health care, home, education, and car. Discretionary spending was going on credit, until that started to bite us in the ass.
This is a good article that explains our current situation
http://www.nytimes.com/2014/02/03/b...eroding-just-ask-the-business-world.html?_r=0
All of the demand and consumer spending is being driven by the top 20%. Thats not good and will have pretty serious repercussions on the economy. An interesting implication that might not be apparent is that it might hinder innovation. Good article explaining it
http://www.slate.com/articles/busin...dy_can_afford_new_products_who_will_make.html
Basically, my point is, is that we need some serious structural changes to our economy to reach 9% growth because we aren't going to reach that if only 20% of the population now can drive demand and consumer spending. We actually need to changes so that the middle class can be apart of that growth like in the past.