
by Kenneth J. Entenmann CFA®
Posted November 19, 2025
“If you build it, they will come.” That famous, whispered line from the movie Field of Dreams seems appropriate for today’s equity market. In April, the market sold off in an overreaction to China’s Deepseek AI model and “Liberation Day” tariff announcements. From Feb. 28th through April 8th, the S&P 500 was down nearly 20%. Since then, it has been on a tear, reaching record high levels multiple times in the Fall. The primary driver of this strong move has been Artificial Intelligence (AI). Indeed, the top 10 stocks in the S&P 500, led by the “hyperscalers” (Microsoft (MSFT), Alphabet (GOOG), META (META, formerly known as Facebook) and Amazon (AMZN)) account for nearly 40% of the S&P 500 market cap! But they also generate 33% of the S&P 500 earnings! The incredible earnings have lifted the Price/Earnings (P/E) ratio of the top 10 to a lofty 32x earnings. The rest of the S&P 500, the other 490 companies, trade at 19.5 and the overall S&P 500’s P/E stands at 23 times earnings. Historically, that is an “expensive” P/E relative to the 30-year average of 17.1 times earnings. Nonetheless, the power and potential of AI have been used to justify the high valuation of the AI universe and the overall market. Don’t worry about high P/Es, this time will be different! The most dangerous sentence in the world!
To be clear, AI does appear to be the next great innovation that has the potential to transform economic productivity. Over the last 150 years, there have been several periods associated with great innovation and high productivity gains. In the late 1800’s, mechanization transformed the economy from an agrarian economy to an industrial economy. The automobile in the 1920s. Post WWII brought electrification and aviation. More recently, the invention of the personal computer, mobile phones and the internet had a dramatic impact on productivity and economic growth.





