about graphic artists and tax accountants. they don't always pay taxes on their income but they're still working, still making a living. they're just doing it off the books. who are the people working in america's shadow economy? it's probably not who you think. >> the shadow economy isn't necessarily comprised of people making $5 here and $10 here. it's designers, computer programmers, tax accountants making tens of thousands of dollars but who prefer to do it off the books. >> reporter: he's a professor of sociology and dedicated his career to studying criminal side of the u.s. economy. he's discovered a growing number of americans working in the shadows are not typically what come to mind when you think of a criminal. >> they may have skills and what they're doing with those skills is not applying for a job in a