Jessica Toonkel for Investment News reports that the success makes the top executives at Vanguard nervous. [November ETF Performance Report.]

The challenge for Vanguard is to maintain momentum once the markets pick up again. The provider has been a leader in low-cost funds, and they believe it will continue to give them the edge as the markets ramp back up.

Out of the battle among providers has emerged one clear winner: the investor.

Tisha Guerrero contributed to this article.