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Goldman Sachs Group is mulling the idea of shutting down its private stock-trading venue, Sigma X, according to The Wall Street Journal.
Sigma X and other so-called dark pools have come under increasing scrutiny after Michael Lewis' new book, "Flash Boys," brought them to light and sparked intense debate over the use of high-frequency trading.
Read More 'Flash Boys' fuels more calls for a tax on trading
According to the Journal, Goldman executives are weighing revenue and risks tied to Sigma X.