The U.S. stock market selloff ushered in the New Year with such a scare that a record 6 million investors called Fidelity Investments asking what they should do with their money.

On Jan. 4, the first trading day of 2016, clients returned from the holidays to face a 276 point plunge in the Dow Jones industrial average that wiped out a good chunk of their portfolio.

Already, retirement accounts at Fidelity ended 2015 lower than a year ago, with average 401(k) balances dropping to $87,900 from $91,300, the Boston-based brokerage firm's latest analysis showed on Thursday.

For the two-thirds of workers who have at least some savings in target-date funds, geared toward a future retirement date, the lower balances raised doubts about their choices.

Target-date mutual funds are managed by professional advisers who adjust the mix of stocks, bonds and cash equivalents based on the selected time frame.

But it can be hard to fight the urge to do something -- anything -- in the face of economic uncertainty.

"They're worried about what's going on with China, what's going on with the election," said Jonathan Kelley, a partner with Hinds Financial Group, a wealth advisory firm in Lakewood, Colorado.

One client called this week, Kelley said, wanting to move everything in his portfolio into bonds and other alternative investments.

Kelley's job on days like this is to talk his clients out of making emotional decisions. He typically creates a mix of investments for them, sometimes with target-date funds and a custom mix that operates like a target-date fund, and sticks with it.

Most investors do the same.