It's a bonafide work force mystery.

And you may have an answer.

First, the mystery.

In researching potential impacts of the "demographic sledgehammer" known as Wyoming's aging population, and in trying to understand rates at which older people leave the work force, the Research and Planning Section, Wyoming Department of Employment, came across something quite unexpected: Between 2001 and 2006, the rate at which people age 45 and older left the work force had accelerated.

Of course, some exits could be attributed to retirement. But the exit rates even among people not yet of traditional retirement age increased.

In the 45-54 age group, for example, the exit rate in 2001 was 4.9 percent; among people the same age in 2006, the rate was 8.7 percent.

About half of those who left the work force turned up working in other states.

Tom Gallagher, manager of Research and Planning, said the change was not explained by an age shift. Nor was it explained by characteristics like gender, industry, earnings or even divorce rates.

Because such factors did not explain the change, researchers looked at broader conditions. In the process, a high correlation was discovered between exit rates and rising home sale prices.

But correlation does not mean cause, so whether one factor is genuinely connected to the other is not clear.

Even so, people age 45 and older increasingly had been leaving Wyoming and taking jobs in another state.

After years, and perhaps decades, of residence in Wyoming, why would middle-age workers in sizable numbers begin pulling up stakes and going elsewhere to work?

Gallagher said there might be some clues in a study of nurses. "As with a majority of the people that work in the state, they're not from here," he said.

Regarding their futures, nurses contacted frequently made comments like, "Don't want to move until my children are out of school," or, "Cannot leave until children graduate high school because of joint custody agreement," or "Will leave when my sons graduate high school."

Gallagher said the degree to which such sentiments among nurses can be generalized to other workers is not known. But perhaps some people have been waiting for an opportune time to leave, and this is it.

With higher homes prices here, and falling home prices elsewhere, maybe it's time to git while the gittin's good.

In an article published in the June 2008 issue of "Labor Force Trends," Senior Research Analyst Sylvia Jones noted that people at the leading edge of the baby boom were 60 in 2006, meaning they would have been 38 during the last oil bust. The memory of those hard times may be tough to shake.

"Therefore, there is the possibility that the effects of the last boom are still being felt in the state today in the form of workers age 45 and older 'cashing out' of the Wyoming market while the state is still in the boom segment of the cycle," Jones wrote.

You may have your own story. Or you may know someone who has recently sold out and taken a job in another state, even as the energy boom continues to roll along.

Send your ideas and comments to tom.mast@trib.com, or to Tom Mast, P.O. Box 80, Casper, Wyo., 82602.

In a couple weeks, we'll see what turns up and compile a follow-up.

Business Editor Tom Mast can be reached at tom.mast@trib.com, or call 307-266-0574.