According to Yahoo Finance, the S&P 500's cyclically adjusted price-to-earnings (CAPE) ratio has remained above 40 for three consecutive months, a level previously seen only before the 2000 tech bubble burst. Historically, the S&P 500 has never recorded a positive three-year return after the CAPE index closed a month above 40. However, the analysis notes that the sample size for this signal is small, and the current market composition, heavily weighted towards high-margin tech companies driven by AI, differs significantly from a decade ago.