Is There Hidden Unemployment?

One of the positive features of the current economic slowdown is that unemployment has not increased dramatically. The unemployment rate remains low by historic standards. But I wonder if there is a hidden unemployment that is not picked up by federal employment surveys and by unemployment claims--that would be the disemployment of illegal immigrant labor. In the Southern Californa housing industry, there were many, presumably illegal, immigrant laborers working as skilled labor. At the height of the housing boom, on numerous occasions, airplanes slowly circled over my Latino/Black neighborhood towing signs in Spanish advertising construction jobs with a phone number to call. Crude printed bills, advertising construction jobs, were also nailed to light poles throughout the neighborhood. I tried occasionally to photograph (for personal and asethetic purposes) housing construction. I was loudly, often vociferously, threatened not to take pictures of workers. I assumed they were illegals. Well, if illegals were not reported as laborers, they probably are not reported as unemployed. Hence, hidden unemployment.