It takes a lot to scare workers into making sudden changes to their 401(k) plans, yet droves of participants moved their retirement assets around last week as the volatile equity markets became too much for many to stomach.

Participants in 401(k) plans fled from equity funds and moved investments into safer fixed-income investments last week as manic market conditions and an uncertain economy rattled many workers, said Pam Hess, director of retirement research at Hewitt Associates.

The firm, whose 401(k) index tracks the activity of 1.5 million plan participants, estimates that these workers moved at least $411 million out of equity investments and into fixed-income funds over the course of several days. In particular, stable-value funds saw inflows of about $320 million last week.

The Hewitt index represents a fraction of the overall 401(k) participant population, which the Department of Labor now puts at roughly 65 million workers. Yet, if the Hewitt index is used as a proxy for how 401(k) participants behaved, then nationwide, all participants would have moved a combined $18 billion out of equity funds and into fixed-income vehicles last week.

“By and large, most participants didn’t panic and stayed put,” said Hess. “But on a couple of occasions last week, transfer activity was much higher than usual.”

And how. On Thursday, September 18, before the federal government unveiled plans for its $700 billion financial industry bailout, more than three times the usual amount of money moved around in 401(k) plans, as every form of equity fund experienced outflows. The Hewitt index registered last Thursday as the second most active day of the year for participants.

The most active was Jan. 22, when the Fed cut interest rates by 75 basis points and the Dow Jones dropped more than 500 points.

Thursday wasn’t the only day last week when 401(k) participants were skittish. Workers transferred 401(k) assets at about three times their usual rate, according to Hewitt, as the Lehman Brothers bankruptcy filing September 15—and the threat of AIG’s demise—prompted participants to trim their large-cap equity funds and company stock holdings.

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

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