The U.S. stock market is surprisingly calm right now…A key reason: a growing divide between mainstream investors, who have largely been sitting out the 2023 stock rally, and the machines whose buying has been driving it…The market’s steady rise has puzzled analysts and portfolio managers as the S&P 500 has churned more than 9% higher this year (and the technology-focused Nasdaq Composite has risen 24%). One explanation: Quant funds, or those relying on computer models and automated trading, have been doubling down on equity markets as other investors have stepped back, citing high valuations and concerns about the likely course of the U.S. economy. – WSJ