Annual turnover among Fortune 500 chief financial officers is at its lowest rate in three years, although CFO burnout is playing a bigger role in resignations, according to a study by Russell Reynolds Associates.

The consultancy’s Financial Officers’ Turnover study, released Monday, May 14, reports that only 13 percent of Fortune 500 companies changed CFOs in 2006, compared with 19 percent in 2005, 16 percent in 2004 and 13 percent in 2004.

In spite of the overall decline in the churn rate among CFOs, the number of CFOs who have chosen to resign is up. The study found that CFO resignations were responsible for 45 percent of the turnover in 2006, up from 32 percent in 2005.

“The regulatory demands on CFOs clearly continued into 2006,” said Chris Langhoff, a member of Russell Reynolds’ financial officers practice. “The time spent on regulatory issues with outside stakeholders has increased dramatically, while the CFO must still support his CEO as a business partner with more traditional financial disciplines.”

No surprise, then, that a change in responsibilities was another leading cause of CFO turnover. A full 20 percent of CFOs left their positions because of this in 2006, up from 14 percent in 2005.

Another factor contributing to CFO turnover is the increasing number of takeovers by private equity firms. A change in chief financial officer is often one of the first moves made by an acquiring private equity firm.

“Private equity firms often appoint CFOs who they know, trust and who have experience turning companies around at new portfolio companies,” Langhoff says. “Thus we expect to see an increase in turnover, especially in private equity-backed companies, in 2007.”

Last year, 17 percent of CFO turnover was attributed to corporate restructurings, up from 4 percent in 2005 and 1 percent in 2004.

Filed by Megan Johnston of Financial Week, a sister publication of Workforce Management. To comment, e-mail editors@workforce.com.