The Nobel Prize in Economics went to three economists including Shiller, who theorized about housing price bubbles and P/E overpricing. I like the graphic that went along with the article and want to access it myself at times so I post it here for anyone's convenience.

Placed next to each other like the New York Times did in another example of their excellent graphics department, one can see how a soaring stock market drives a housing bubble. The drop we saw in 2006 was predicted and we still seem a little high so don't get that second mortgage to finance your child's education just yet.