"Well, we only have estimates ... and they suggest that there is a 15 percent underreporting of taxable income," says Dr. Walden, an N.C. State University professor and extension specialist. "So you could call that 15 percent tax evasion.

"Very interestingly the percentage is lower for income taxes, I think one reason being we have withholding for income taxes," Walden adds. "It's much higher for investment income, where there is no withholding.

"Also, the underreporting of income by large corporations is much lower than for small ones. Some people may think that it would be flipped around, but large corporations don’t engage in as much tax evasion, so called, as small ones.

"But all in all, the 15 percent under-reporting ... really to me as an economist indicates a remarkable degree of compliance with the tax code," he concludes."