The existence of hidden income has expanded the income gap remarkably, in our opinion.

FORBES: The Chinese Have $1.5 Trillion In Hidden Income

If anything, Social Security and Medicare should be expanded to cover the huge gap in retirement savings and health care coverage.

FORBES: Fiscal Cliff Follies: Four Myths

Developed at Wagner's request at a time when the technical capabilities of modern brass instruments were being expanded, it enabled him to fill a gap in tone color between the mellow lyricism of the horns and the penetrating brilliance of the trombones.

WSJ: It Takes Brass to Play the Wagner Tuba | By Barbara Jepson | The Ring of the Nibelung

For individuals, the healthcare knowledge gap needs to be closed through systematic, expanded access to healthcare education for K-12 children and adults alike, perhaps through online and other channels.

FORBES: The Other Healthcare Divide: Healthcare Fluency