How effective are activist hedge funds at forcing change upon — and boosting value — at the companies they target? Pretty effective, researchers at Wharton and three other business schools report in a new research paper, "Hedge Fund Activism, Corporate Governance and Firm Performance." As earlier noted Thursday in a piece on the sale of Pentax Corp., the phenomenon is reaching parts of the world that previously seemed off limits, such as Japan. And just the scope of this paper shows what a significant force the funds have become: The study looked at 888 cases involving shareholder activism by 131 hedge funds from the start of 2001 through 2005. Read on to find out more.

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