To top this off: there are plenty of periods that actually exist in history where you could make this statement "The fed expanded the money supply by x% last year. That money supply inflation is believed to helped encourage the x+1% growth over the same period." Maybe they're not as common, maybe it's a sign of a bubble, but the fact remains that you cannot say for certain that the same cause always has the same effect. There are WAY TOO MANY VARIABLES. In the same vein, you can't be sure the same effect has the same cause. So the cause has to be separate, without bias and analyzed on its own merit.