Once a lowly underdog in the mutual fund space, investment company Vanguard has become a behemoth with over 30 million investors led by an army of “bogleheads” (index investing enthusiasts and disciples of Vanguard founder and investor advocate John Bogle).

The sheer magnitude of the lead that Vanguard has amassed over its competitors has been documented by research provider Morningstar in a new report.  Morningstar points out in its executive summary that Vanguard’s market share is greater than that of its next three biggest competitors combined (that’s for both mutual fund and exchange-traded funds).  Furthermore, Vanguard’s lead continues to expand.

Over the past year, Vanguard has attracted nearly half of all mutual fund and ETF inflows.

Crowded trade risks, while often unappreciated by investors, can be real and significant. They can be viewed as a byproduct of the immense proliferation of index and index-like products. While these products meet important investor needs, their predominance has led to market conditions that can greatly intensify selloffs-and could expose equity managers to greater than expected losses in the event of a market downturn.