(information contained in this website do not constitute investment advice, I’m not a financial professional…)
The Shiller PE Ratio is one of the tools that I like to refer to feel the health of the market. The ratio is an average of ten years of price-to-earnings and adjusted for inflation. I believe that this ratio is one of the most relevant to see if the market is undervalued or overvalued. Do not forget that this data is valid mainly for the American market, given the fact that it calculates the P / E 10 of the S&P 500. I advise you to read Irrational Exuberance from Robert Shiller to dive deeper in the subject. He is one of the most fascinating teachers I have had the chance to study with. You can take an introductory course online with him on Coursera at coursera.org/learn/financial-markets-global.