Nearly two-thirds of Americans say they are more worried about running out of money in retirement than dying, and many retirees could be on track to turn that fear into a stark reality.

About half of America’s retirees don’t take any systematic approach to withdrawing their many billions of dollars in retirement assets, according to an October survey from IRALogix, a retirement technology firm. Just 22 percent of retirees follow any kind of plan.

“You can’t just arrive at age 65 or 67 and say, ‘OK, now what am I going to do?’ It’s a process, not an event,” said Peter de Silva, chief executive of IRALogix. “It’s coming. You’ve got to plan for this.”

Working from a plan becomes crucial if stock prices plummet in the early years of your retirement, when taking withdrawals during just a few years of down markets can put you at risk of running out of money. Data from the Bureau of Labor Statistics shows that people 65 and older consistently leave the work force when stocks go up, and rejoin it when markets drop, while a 2024 T. Rowe Price report noted that about 10 percent of retirement-age Americans say they have to work for financial reasons.

“Even those that have a plan don’t adhere to it, so it’s a plan in name only,” said Kelly LaVigne, vice president of consumer insights at Allianz Life. “You’re going into 30 to 35 years of giving yourself a paycheck and you don’t have any idea whether you’re going to make it.”

The classic approach

If investors know anything about structuring retirement withdrawals — what financial planners call “decumulation” — it’s the 4 percent rule. This was posited in 1994 by a financial planner, Bill Bengen, who reviewed market returns dating back to 1926. Mr. Bengen found that even during the worst three decades for stocks — from October 1968 to 1998 — a retiree withdrawing no more than 4 percent of his or her balance in the first year of retirement and adjusting subsequent withdrawals for inflation would have money left after 30 years.