And to corporate cost cutters, the thinning ranks might not seem like such a bad thing, especially in industries such as manufacturing where jobs continue to move overseas.

"A lot of companies do welcome the chance to have older workers leave, especially those with seniority-based pay systems, because they can be replaced with cheaper workers," says Peter Cappelli, a management professor at the University of Pennsylvania's Wharton School.

Still, retirements don't necessarily substitute well for layoffs, Ashworth says.

"You're no longer targeting who you're losing, and you're losing your most experienced people."

Some experts think the impact won't be as stark as the numbers suggest. Fully 70 percent to 80 percent of baby boomers expect to continue working in later life, several studies show. And amendments to the federal Age Discrimination in Employment Act outlawed age-based mandatory retirement in most industries in the 1970s. The upshot: most boomers can work as long as they like, barring layoffs. "Right now I have no plans to stop," says Leola Williams, a 73-year-old housekeeping manager at Baptist Health South Florida Inc. in Miami.

Still, many companies simply don't know how many of their workers plan to retire, and when — in part because they fear that asking will open the door to age-discrimination claims, says Jeri Sedlar, co-author of the Conference Board's report. There are no federal rules against asking employees retirement-related questions. But the formal collection of such information could be used as fodder in a lawsuit if a company later laid off, fired, demoted or failed to promote the workers who had been surveyed.

Some companies have sidestepped these concerns by querying workers anonymously or asking employees of all ages about their plans five years from now, says Linda Barrington, research director at the Conference Board.

In fact, when the Platte River utility decided to poll its employees about their exit strategies, "we reassured them ahead of time that we were not planning their retirement parties," says Green, the human-resource manager.

Some companies that are concerned about a wave of retirements are getting creative, including offering programs that let employees technically retire, yet stay connected to their employers.