“Over the last couple decades, investors have poured trillions and trillions of dollars into index funds and other massive funds run by three companies: Vanguard, BlackRock, and State Street Global Advisors, which together have over $16 trillion in assets under their control. If you have a retirement account, there’s a good chance it’s run by one of them. Their combined average stake in each of the biggest 500 American corporations (aka the S&P 500) went from 5.2% in 1998 to 20.5% in 2017. As we’ve written before in the Planet Money newsletter, legal scholars and economists are increasingly concerned as these gigantic institutional investors gobble up greater and greater stakes in companies within the same industry.” Is Your 401(k) Colluding To Make Cereal More Expensive? (They’ve been … no, Dave, don’t do it … milking us for years…)