The five largest institutional, tax-exempt U.S. fixed-income index asset managers had assets under management of $838.2 billion as of June 30, according to Pensions & Investments' annual survey. That accounted for 86% of the category's AUM. A decade ago, the same five managers had an AUM of $289.8 billion, or 61% of the reported total.
Vanguard Group had $312.7 billion of AUM vs. $85.3 billion in 2013. State Street Global had the second-highest AUM, at $177.5 billion, double 2013's $88.7 billion.