Please skip if you're not into this.

So, I've been trying to make sense of Robert's Schiller's PE theory. The basic, layman gist that I am currently understanding is that if the market always regresses to the mean, then it's a matter of calculating how far the market is currently off from the mean right?

Now, Schiller is a smart guy. I don't deny that. It's just that... well, there's a lot of controversy surrounding the question of HOW effective this sort of back-testing is. Could 10 years, or 20 years, or 30 years of historical market performance give us an insight as to whether the current market is over-bought or over-sold? (Remember me talking about a serious investment troll? Yeah, that's what this is about, and I hope he doesn't find me here.)

Ignoring the issue of what exactly does "predictiveness" mean for a second, I came across a study that suggests that while PE/10 (/20, /30) has some predictiveness, there is another measure, Tobin's q, that is much more predictive.

Now, if you do buy into this, both Schiller's PE and Tobin's q suggest that the market is supposedly, as of the month of June, over-valued at somewhere around 15%. Not exactly beaming news for traders. (I'm still buying and holding though.)

Anyways,