Dude.

Dude.

We're talking business majors, that didn't go into accounting, whose primary skill is buying and selling something designed to be bought and sold, whose job it is to predict when things are bought and sold. Remind me - did you read Piketty? Did you notice how every time he resorted to algebra he apologized profusely?

Yeah - Schiller got a Nobel for CAPE ratios. Which are literally inflation-adjusted profit-to-earnings.

but how are we supposed to do that, egghead?

To calculate P/E10:

Look at the yearly earning of the S&P 500 for each of the past ten years.

Adjust these earnings for inflation, using the CPI (ie: quote each earnings figure in 2017 dollars)

Average these values (ie: add them up and divide by ten), giving us e10.

Then take the current Price of the S&P 500 and divide by e10.

Why ten? Because fuck you, that's why. Anybody in economics serve ten year terms? Anybody in politics? It's too long for tequila and wine, too short for every scotch but one (holy shit: Laphroag is the secret underlying economic research!) and only makes sense in terms of "well, why not ten."

But ignore that for a minute. Did you see the part where they explained how to take an average? Do you see that often?

The only place I'm used to seeing them explain averages for schlubs who might not remember 5th grade math is economics sites. And then they usually throw some crazy fucking curve up there and start talking about Elliott Wave Theory or some shit.

You are now aware that the US Federal Reserve makes most of its predictions and prognostications based on the Phillips Curve. Check out the higher-order math on that guy. I mean, shit. It's got subscripts and superscripts and lambdas and all sorts of crazy mathy stuff but dig into it, and it's basically a bunch of bullshit coefficients having a fight to yield a correlation.

Math is like the catalyst in economics. It is essential in order to make it happen but it is neither consumed nor destroyed.