(Bloomberg) -- Fidelity Investments, the second- largest mutual fund company, is exploring the creation of a U.S. stock trading venue along with other investors to address perceived flaws in the $23 trillion U.S. equity market.

The venture under consideration would aim to “address today’s market structure, and provide higher levels of transparency, liquidity and control for the benefit of all fund shareholders,” Vincent G. Loporchio, a senior vice president at Fidelity, wrote in an e-mail today. “However, it is premature to discuss details at this time.”

U.S. stock trading is spread across more than 50 exchanges, electronic venues known as dark pools, and internal platforms at broker-dealers. The complexity this fragmentation causes was highlighted in Michael Lewis’s latest book, “Flash Boys,” which has sparked more than a week of debate over whether investors are treated fairly in the world’s largest securities market.

The central characters in Lewis’s book formed IEX Group Inc., a dark pool that aims to neutralize advantages that high- frequency traders purportedly have when they buy and sell shares with investors big and small. Dissatisfaction with the status quo prompted the Investment Company Institute, the trade group for money managers with $17 trillion in assets, to organize a series of meetings last year to give money managers, broker- dealers, exchanges and market regulators a forum to discuss their concerns, Bloomberg News reported in December.

Stepping Forward

While there has been progress toward improving the structure of the U.S. stock market, “clearly there are some things that can be improved,” Walter Todd, who oversees about $990 million as chief investment officer of Greenwood Capital Associates LLC in Greenwood, South Carolina, said by phone today. “Maybe this is a step towards that,” he said, referring to Fidelity’s potential venue.

IEX Group is gaining traction. It handled 23.9 million shares yesterday, up 27 percent from the daily average in March. While IEX accounts for less than 1 percent of total volume, the five-month-old platform has more trading than four of the 13 American exchanges, including IntercontinentalExchange Group Inc.’s NYSE MKT.

Shareholders of IEX Group include some of the most high- profile money managers: David Einhorn’s Greenlight Capital Inc., Bill Ackman’s Pershing Square Capital Management LP, Capital Group Cos. and Brandes Investment Partners.

Fidelity’s trading division already runs a dark pool called CrossStream.

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