The total sum of these individual areas thus represents the total area under the curve.

FORBES: Apparently, Calculus Was Invented In 1994

Other factors also exaggerated the income increases in the two months, including lump-sum benefit payments handed out in December, and the loss of income for many in the New York area during October because of disruption from Storm Sandy.

BBC: US personal incomes jump ahead of New Year tax rise

The euro area also has its temporary rescue fund, which will lend the Spanish government the initial sum of money for the banks.

ECONOMIST: Spain and the markets