Historically, the PE for the entire U.S. stock market is about 15. But today’s market PE of roughly 23 is about 50 percent higher than the historic average Every time I see statements about the PE of the market, I wonder which PE they mean? The price of the companies divided by their past revenue? If so, which past? Last month, last quarter, last year? The price of the company divided by future revenue? Then future r…
"The PE ratio of the S&P 500 divides the index (current market price) by the reported earnings of the trailing twelve months."
So it's current total market value (add the market cap of all 500 companies in the index),
And divide by the total past 12 months earnings of the same 500 companies.
If that doesn't answer your question, please let me know.