That twice-monthly survey is separate from the consumer confidence index produced by the private research group the Conference Board.
Thomson Reuters pays for exclusive access to the University of Michigan results, and some of its clients have been paying extra to receive the data two seconds before other clients receive it at 9:55 a.m. This allows high-speed computers to make trades before others gain access to the data.
Thomson Reuters then sends out a news release about the survey at 10 a.m.
Modern stock trading is dominated by automated computer systems that make trades in fractions of a second, and traders can profit from receiving data even milliseconds before its public release. Consumer sentiment regarding the economy is watched closely because consumers' spending accounts for about 70 percent of U.S. economic activity.
The attorney general's office said in a statement the two-second edge that Thomson Reuters gives to some high-frequency traders amounts to an unfair advantage as those traders "execute enormous volumes of trades in the blink of an eye."
"The securities markets should be a level playing field for all investors and the early release of market-moving survey data undermines fair play in the markets," Attorney General Eric T. Schneiderman said in the statement.
Thomson Reuters said separately it "strongly believes that news and information companies can legally distribute non-governmental data and exclusive news through services provided to fee-paying subscribers."
"It is widely understood that news and information companies compete for exclusive news and differentiated content to help their customers make better informed trading and investment decisions," the Thomson Reuters statement said.
Company spokeswoman Yvonne Diaz added that Thomson Reuters has always been transparent about how it releases proprietary data so its customers can choose the level of service they want.
Last month, the Conference Board announced that it will no longer provide its economic reports in advance to news organizations because it suspects the data is being diverted early to computer-driven trading systems, which can unfairly profit from it.
It had long provided its monthly data to reporters 30 minutes before the information is publicly released. That early access allowed journalists to prepare news reports ahead of the information's public release.
Last year, the Labor Department revoked early access to its employment data for several companies that deliver data to high-speed traders but produce little or no original news content.