A Canadian securities regulator backed away from praising high-frequency traders just hours after endorsing their role in the market.

The Investment Industry Regulatory Organization of Canada had commissioned a series of academic studies about HFT, and summarized their findings in a statement Wednesday. The initial news release said HFT -- an often-criticized practice of buying and selling in tiny fractions of a second -- has had a “mostly positive” effect on the Canadian stock market. Later in the day, the regulator reissued the statement, omitting “mostly positive.”

The new statement still contained bullet points that boiled down the conclusions of the studies, including positives such as improving liquidity and market prices as well as saying there’s little evidence fast traders cheat, or front run, slower ones. But the overall evaluation that HFT is helpful disappeared.

“We erred in the press release we issued yesterday,” Lucy Becker, a spokeswoman for IIROC, said in an e-mail Thursday. “The only conclusion that IIROC has made with respect to HFT is that the results of the study did not reveal any concerns that warranted a regulatory response beyond measures already implemented by IIROC. As a regulator, it is not our role to judge whether or not HFT is positive or negative -- it is our role to ensure that markets operate in an orderly manner and with integrity.”

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