Asset managers are ubiquitous absentee owners who own large stakes in literally every major firm in the economy. The big funds - Vanguard, Blackrock, State Street - "buy the whole market" (a big share in every top-capitalized firm on a given stock exchange) and then seek to deliver returns equal to the overall performance of the market. If the market goes up by 5%, the index funds need to grow by 5%. If the market goes down by 5%, then so do those funds.
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