"If we look at the top 1 percent of Americans by income, they now receive 15 percent of all income in the country," says Walden, an economist with the North Carolina Cooperative Extension Service at N.C. State. "This is up from 8 percent 30 and 40 years ago.

"Most of this increase, interestingly, is due to increases in their labor income -- income they earn by working -- not their investment income," he observes.

"But perhaps surprising to some ... you see the same trends in the U.K. and also in Canada," Walden adds. "You don't see, however, these trends toward a large increased income going to the super rich in continental Europe and in Japan.

"So a big question among economists is, 'Why?' One answer -- there are no definitive answers -- but one answer is that in countries like Canada, especially the U.S. and the U.K., there is a more open and less restrictive economy that has allowed greater rewards to go to top managers and executives."