Those falling Idaho unemployment rates — from 7.7 percent to 7 percent — over the past five months don’t mean that a lot more people in the state are earning paychecks. It means the size of the workforce — people with jobs or looking for work — shrank from 781,876 to 774,931.

How did that happen? Experts are not sure. But there are theories.

Extended benefits disappear: Congress strengthened a safety net for laid-off workers after the Great Recession began, extending jobless benefits up to 99 weeks. But that extension has grown steadily shorter and will disappear by the end of December. To receive benefits, you must look for work. When their benefits end, some people may be ending their searches.

Retirements: Older Idahoans who may have lost their jobs in the recession may be deciding to retire after trying in vain to find work.

Also, the state’s aging workforce means more people are ending their careers than are coming into the workforce.

Dual incomes: Some families may have had two incomes and lost both, so two people were seeking jobs. One could have found a job while the other stopped looking.

Statistical error: Workforce numbers are calculated from a survey of 600 Idaho households each month. Among the questions people are asked is whether they are working or looking for work. The size of the survey sample is small, which can skew the results, said Bob Uhlenkott, chief researcher officer for the Idaho Department of Labor. When the U.S. Department of Labor refines and updates its 2012 data early next year, he expects the 7,000 number will shrink.

If you or someone you know has left the workforce after your unemployment benefits ended, and if you’re younger than retirement age, we’d like to hear your story. Contact the writer of this Biz Buzz:

Bill Roberts, 377-6408, broberts@idahostatesman.com.