WASHINGTON (Reuters) - Federal Reserve Chairman Ben Bernanke, criticized for statements some investors have found confusing, has indeed moved financial markets more than his predecessor Alan Greenspan, according to a recent study.

But the research, by former Fed Governor Laurence Meyer and former senior Fed economist Brian Sack at Macroeconomic Advisers, noted Greenspan also unintentionally provoked sharp moves in financial markets from time to time, in a reminder that Fed communication has always been prone to risk. Current Federal Reserve Chairman Ben Bernanke "Bernanke is dominating the committee in terms of market effect. He has accounted for 27 basis points of movement in two-year yields, about 3-1/2 times the effect of the next most influential FOMC

[Federal Open Market Committee] member.

"This difference is starker than that observed in 2005, when then-Chairman Greenspan was less than two times as influential as the next member," said the study, which was published earlier this week.

Movements in yield on the two-year Treasury note are measured from 15 minutes before individual FOMC members' speeches or testimonies and for two hours afterward.

Bernanke, who took the reins from Greenspan on February 1, has unsettled some market practitioners by making comments that were interpreted as dovish and then apparently correcting this impression in subsequent remarks.

"Market participants have been surprised to have the Chairman being so directional in his comments, especially at a time when policy is so data-dependent," the study noted.

On the other hand, an examination of Greenspan's record found he had also caused significant volatility during his tenure and on occasion was forced to backpedal from his own words.

In a June 11, 2002, speech, Greenspan's warning of significant risks to near-term growth was seen by futures markets as increasing the chances of a quarter-percentage-point rate cut at the next meeting to 64 percent from 24 percent.

But the chairman later that month admitted in remarks designed to rectify the initial impression that he had not chosen his words with sufficient care.

"The bottom line is that the volatility induced by the recent communications events is not unprecedented. One does not have to look far back in Greenspan's tenure to find an episode when he moved markets even more sharply in either direction.

"Hence, the recent events under Bernanke may speak more to the general challenges of central bank communications than to the specific abilities of the new chairman," the study said.

Scrutiny of the FOMC effect on financial markets is a regular effort by Macroeconomic Advisers.

Their current study found that St. Louis Federal Reserve Bank President William Poole and Chicago Fed chief Michael Moscow were the next two biggest movers after Bernanke.

Poole was already up there in the last survey, but Moscow has increased his impact, as has Richmond Federal Reserve President Jeffrey Lacker, Dallas Fed President Richard Fisher and Kansas City Fed President Thomas Hoenig, the study noted.

With several hundred speeches from FOMC members every year, the league table helps investors concentrate on the comments of individual policy-makers who are more prone to move markets than other central bank officials.