Here, then, are some relatively recent purchases made by some billionaires. Indeed, UnitedHealth has been offering promising news lately, including meeting its Medicare Advantage plan enrollment targets. Despite its huge size, recently valued at $2.5 trillion, it's still growing at a respectable clip, posting second-quarter results that featured net sales up 13% year over year. Speaking of AI, Ackman recently had 45% of his portfolio in three AI stocks, and Alphabet is one of them. Instead, the company has been using AI as a tailwind, with search revenue growth actually accelerating recently.