Warren Buffett’s Berkshire Hathaway (BRK.A) (BRK.B) portfolio is one of the most closely watched on Wall Street. The Oracle of Omaha is a master of buy-and-hold investing, and over his 60-year tenure, he transformed the struggling textile company into a powerhouse conglomerate with a market capitalization of more than $1 trillion. Under Buffett’s leadership, Berkshire owns positions in dozens of stocks—and what he invests in matters. When Berkshire Hathaway disclosed taking a new position in UnitedHealth ...