In the depths of a bear market that has carved between $500 billion and $2 trillion from U.S. retirement accounts so far this year, as many as two-thirds of all Americans have stopped contributing to their retirement plans, a new study shows.

And that’s precisely the wrong decision to make at the wrong time. No matter how poorly the financial markets are performing, saving for retirement has to remain a top priority.

“It’s not a time for people to stop contributing,” Diane Young, director of retirement and goal planning at TD Ameritrade Holding Corp. (AMTD), the Omaha, Neb.-based brokerage firm that conducted the retirement study, said in an interview with Bloomberg News. “Because time is money, it’s important to stay on track.”

According…