A chunk of the workforce evaporated during the Great Recession

Participation is everyone who is working plus everyone who wants a job.

Compare the early 1980s recession to our current situation. You can see why unemployment was so high, as a number, in 1982-1983. Jobs disappeared but nobody left the work force (blue line steady). Hence high number of people who said they were seeking employment but not finding it.

In the great recession, 3% of the population appears to have just checked out. What has been narrowing the gap (reducing unemployment number) the last few years is the blue line going down, not the black line going up.

If the work force participation rate had stayed flat the official unemployment number would have zoomed up to 10-11-12% and then stayed in that range for years on end.