Interesting Paper from GMO on Bursting Stock Market Bubbles and Anti-Bubbles

Here is the paper. Yes, they think that we were in a bubble in 2017 and much of 2018 and the last quarter of 2018 was the beginning of the bursting of the bubble. The problem with the CAPE measure of valuation they use is that it is so backward-looking. If profits are growing fast, CAPE will be high because it uses the average profits of the last 10 years. It has the built-in assumption that profits growth is very strongly mean-reverting.