(Bloomberg News) -- While Washington has long been debating how to reform big Wall Street banks, Vanguard is quietly doing just that as the company and its army of index funds takes about $20 billion a year in revenue from the financial industry.

So far in 2015, Vanguard is leading a record $365 billion in net flows into low-cost and passively managed index funds and ETFs, according to Bloomberg data. Meanwhile, the active mutual funds that constitute some of Wall Street's best customers have lost $147 billion, according to the Investment Company Institute. That adds up to about a half-a-trillion-dollar swing so far in 2015, which will be the most ever in a year.

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