The Bureau of labor Statistics compiles a stat called the Employment-Population Ratio that is the number of people working of the available workforce, defined as people 16 and over. I am sure some of those folks are not working because they wouldn't otherwise, but in the current climate many have no choice. As has been reported repeatedly, the 9.2% unemployment underestimates the number of people unemployed because after a long enough time people just leave the workforce and are not counted in the number. The chart below shows the current ratio is 58.2%, that's the lowest Employment-Population ratio since 1984.
A longer time series shows the history since 1948.
It's been lower in the past, but that is a generation ago. I personally would like Congress and the President to start working on jobs now.
(Unstable Isotope at Delaware Liberal got me thinking about this)