[ryansmccoy]

It's a little complicated because all these metrics are like trying to compare apples, oranges, and bananas. So, it depends, and it's not necessarily the best metric to gauge the valuation of the markets.

It's price divided by earnings.

For price, I believe it's the sum of the market capitalization of all the companies in the S&P 500. If you divide by shares outstanding for all the companies, then you get price of the S&P 500 (price).

For earnings, is the sum of all the companies earnings (Net Income) in the S&P 500. If you divide earnings by shares outstanding, then you get earnings per share (earnings).