I think you'll find the whole valuation of the S&P500 is built upon retirement accounts. Yours. Mine.

In other words, look one level deeper and you'll see it's not the S&P500 that's overvalued. It's you and me and 100 million other people desperately attempting to make sure young people pay for them for 20-30 years when they're old.

And then you calculate it out ... and see it's not happening. No matter what the number on the account says.