"Unemployment Rate Reached a Record Low in 19 States Last Year"[1]
[0] https://www.usnews.com/news/business/articles/2019-04-04/app...
[1] https://www.bloomberg.com/news/articles/2019-01-23/unemploym...
https://www.census.gov/newsroom/blogs/random-samplings/2016/...
I would expect percentage of employed over age of 18 to be declining simply because the number of people retiring (or unable to work due to age) is greater than # of entering labor force.
For example, Georgia is the second youngest state with only 9.6% of the population over 65 years-old, but they have a below average laborforce participation rate of 62.8% [1]. Pennsylvania, with 15.6% of the population over 65 is the second oldest, but has a 62.9% participation rate.
Iowa is the 4th oldest state and has the 6th highest participation rate (68.8). North Dakota is 5th oldest and 3rd highest rate (69.3%). South Dakota is 8th oldest and 7th in LFPR (68.7%).
Because they don't need to work. They're not applying for unemployment and they're not taking jobs. So, logically, they're using their time on non-work-related activity. They're having fun, or otherwise doing stuff that they would rather do than work.
The media has this terrible tendency to promote work as the primary marker of life success, which is a valid opinion, for sure, but it's not a universal one. Some people step out of the workforce because they can, and good for them. I expect the wealthier our society becomes, the more people will have this opportunity.
Say that to the workers that got laid off, lost earnings and perhaps even the health insurance their family depends on.