In 1991, earnings fell 14.8% while stock prices rose 26.3%. The result: a multiple expansion of over 48%, moving the P/E ratio on the S&P 500 from 14.6 to 21.6.
In 2020, earnings fell 22.1% while stock prices rose 16.3%. The result: a multiple expansion of over 49%, moving the P/E ratio on the S&P 500 from 20.6 to 30.7.
When changes in prices exceed changes in earnings, multiples expand. When changes in earnings exceed changes in prices, multiples contract.