(Bloomberg) -- Vanguard Group, which has grown into the world's largest mutual fund manager by offering low-cost investments, is prepared to cut fees further as it seeks to increase market share and boost investor returns in an environment of modest returns.

"We're built to take advantage of economies of scale in this business," Vanguard Chief Executive Officer Bill McNabb said during an interview Tuesday at a Morningstar investment conference in Chicago. "And where we see economies of scale, we pass them onto the investors in the form of lower fees."

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