Nasdaq is also battling competitive forces at home, including an upstart Kansas City electronic network known as BATS Trading, which has siphoned some 15% of the matched and routed orders from Nasdaq in its own listed shares.

FORBES: Agita On Wall Street

Whenever two orders are matched, the system automatically records the transaction and sets up the paperwork for its completion.

FORBES: Electronics Communications Networks (ECNs)

Orders are anonymously matched and not reported to any entity, even the regulators (Younglai and Spicer 2009).

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Now, partly thanks to flash orders, Direct Edge is the third-largest stock trading platform by matched volume in the country, according to Raymond James.

WSJ: Ban on Flash Orders Is Considered by SEC

Specialists are supposed to make orderly markets in stocks by matching buy and sell orders, dipping into their own firms' capital when buyers can't be matched and selling firm inventory when there are too many buyers.

FORBES: 's Chief Executive Kenneth Lewis