Bloomberg:  The Big Three—BlackRock, Vanguard, and State Street—are the most important players in corporate America. Whether they like it or not. “If you hold a stock market index fund, congratulations. The S&P 500’s total return was a thumping 31.5% in 2019, and a fund that passively tracks that benchmark delivered almost all those gains, minus a tiny fee—perhaps just 0.04% of assets. Now here’s something you probably weren’t thinking about when you clicked on the box to choose an index fund in your 401(k) or IRA: You were also part of one of the biggest shifts in corporate power in a generation. The index fund is one of a handful of unambiguously beneficial financial innovations. Before it caught on, investors routinely paid sky-high fees to active stockpickers who often delivered subpar returns. The near-universal popularity of index funds puts them up there with Social Security, Stevie Wonder, and streaming TV. Indexing also has been a runaway success for some fund companies. The largest asset manager in the world, BlackRock Inc., best known for its iShares brand of exchange-traded index funds, has $7 trillion under management. Index pioneer Vanguard Group Inc. has $5.6 trillion. The No. 3 indexer, State Street Corp., manages $2.9 trillion. These companies also run active funds, but together they hold about 80% of all indexed money. They’ve come to be known as the Big Three…”