Alex Tabarrok at Marginal Revolution posted this chart 3/19/16:
The thesis here is that instead of moving to find new jobs when a geographic area was decimated (which you can see did happen in the late 70’s,) people opted to drop out of the workforce entirely during the most recent recession (often by retiring early or going on disability).
The comments section has a lot more speculation as well, involving the “global workforce,” illegal immigration, women in the workforce, the extension of unemployment insurance, the housing market collapse, demographics, and even occupational licensing.
I think it’s a lot more complicated than that, but includes all of it. It’s interesting how the rate of migration slows dramatically when the recession hits, then jumps up as the economy improves. This is true for the 1980 & 1981 recessions, as well as 2000 and 2008.