How to assess if equity investment is expensive?

One of the measures closely watched is a 12M forward P/E (how much of a price you are paying for 1$ of future earnings). Chart shows 10-year distribution of 12M forward P/E across different regions.
For comparison 12M forward P/E: Apple: 32, Tesla: 333, Facebook: 28, Amazon: 131, Alphabet: 29, Berkshire Hathaway: 13, Netflix: 61, FAAMG aggregate (2020): 32, Tech bubble aggregate (2000): 55.

(Chart source: Goldman)

Deni Memic

Academic Program Chair Finance at Higher Colleges of Technology - UAE