The S&P 500’s Shiller P/E has reached 41.48, putting the market back in valuation territory previously seen only around the dot-com bubble. The all-time monthly record is 44.19, set in December 1999.
The monthly series begins in 1871 and has a long-run average of 17.42. Today’s reading is approximately 2.4 times that historical norm. Just 16 monthly observations were higher than 41.48, and all of them occurred during 1999 or 2000.
The ratio has registered 40 or higher in only 26 months. Twenty-one were recorded from January 1999 through September 2000. The remaining five are May through September 2026.
CAPE compares the index price with the average of the previous 10 years of inflation-adjusted earnings. That design smooths temporary profit swings, but it also means the ratio should be read as a long-term valuation measure rather than a short-term trading signal.
The historical comparison is sobering without being a forecast. After the market peaked in March 2000, the S&P 500 declined roughly 49% and the Nasdaq fell about 78% by October 2002. Today’s earnings backdrop, sector composition, interest rates, and accounting environment are different.
High starting CAPE readings have historically been associated with lower long-term real returns, but they have not reliably identified the exact month when a bull market ends. The current reading shows how much future growth is already reflected in $SPY and $QQQ, not when that optimism will reverse.