The Great Recession changed a lot of things in corporate America. The biggest adjustment came when business decided to cut the number of full time workers so they could rely on cheaper parttime seasonal labor when demand increased. But that's just one factor.
Pay attention Republicans, because recent analysis explains why labor participation rates are lower, and have been trending that way for some time. Brookings Institute:
The disappointing trend in participation is almost certainly linked to longer term trends in society and the economy that have pushed down participation rates among prime-age men and, more recently, prime-age women. The President’s Council of Economic Advisors recently analyzed the long-term trends (here and here). It notes that most of the participation decline since 2007 has been concentrated among men. This is not surprising, since the prime-age male participation rate has been trending downward since the mid-1950s.
Some of the long-term decline in this country is traceable to declining employer demand for relatively unskilled workers engaged in physically demanding jobs. Part of it, too, is the result of shifts in family living arrangements and in women’s role in the labor market, both of which have reduced the central role of prime-age men as the principal breadwinner of a family. (Also) many Americans entering employment every month were jobless and did not report looking for work in the previous month.