Personal income in the U.S. showed a substantial increase in the month of December, according to a report released by the Commerce Department on Thursday, although the report also showed a slightly smaller than expected increase in personal spending. The Commerce Department said personal income surged up by 2.6 percent in December following an upwardly revised 1.0 percent increase in November. Economists had expected income to climb by 0.7 percent compared to the 0.6 percent growth originally reported for the previous month. The report also showed that personal spending edged up by 0.2 percent in December after rising by 0.4 percent in November. Spending had been expected to increase by about 0.3 percent.