eherlihy , you are absolutely right.
The Labor Force Participation Rate on
U.S. Bureau of Labor Statistics site provides the most insightful data that I have seen. I've been using it to sanity check the spin doctors. It is not pretty picture. especially given a reduced immigration rate and many deferred retirements.
The Labor force size should also be available. But, I have yet to see stats on the under-employed. Iirc, you can get the actual definitions for the various rates on this site.
Best Wishes.