A startling number of baby boomers are refusing to leave the workforce.

And that’s going to have an impact on everyone in younger generations wanting to replace them.

In fact, people over 65 are staying in the workforce at a rate not seen in more than 50 years.

Why? It’s anyone guess since the Labor Department doesn’t ask people the reason they are still working, only whether they are.

Here are some numbers:

As of May, 19.8 percent of Americans age 65 and over told the government they were still working. That’s a figure you get from the Labor Force Participation Rate, and it’s buried so deep in the government’s numbers that you need the help of a data archaeologist to find it.

The participation rate of those older than 65 was only, for instance, 10.8 percent in the summer of 1986. And for decades, the figures stood at around those levels.

In 1960 — before the age of 401(k) retirement plans, stock market booms and such — 20 percent or more of the over-65 population was still participating in the labor force.

What could be causing people to remain in jobs longer now? I can guess. One factor might be that interest rates have been low for so long that savings aren’t generating enough income for potential retirees.

Also, people are probably healthier these days and see themselves living longer, which might make them think there is still plenty of time to putter around in the garden or play with the grandkids.

It might also be that the last recession — the Great Recession — put the fear of God into boomers, who might not think that any amount of savings is enough to tide them over until their final days.

Jobs could also be so plentiful that workers are begging people not to retire — although I doubt that’s the case.

There’s no way of knowing from the government stats whether the 65-plus set are staying in the same job or getting part-time work. But no matter which reason accounts for it, if people are filling jobs longer, that leaves fewer positions for younger people just starting out or middle-aged workers trying to keep up their lifestyle.

If this trend continues, and it has been growing stronger since the beginning of the year, it will have a profound effect on the labor markets.