Update: I had completely forgotten that reader AJK had provided detailed return analysis going back to 1950 on the same topic, so credit to him for this post...
In response to my post on gold vs. equities, Irrational Doomsday stated:
That's good. I think the next logical step would be how far investment returns can diverge from real underlying economic growth (ie Real GDP growth).
As requested... it's not too surprising that in recent years the real returns of the S&P 500 has been highly correlated to real economic growth.