The Conference Board’s index increased to 56 from a revised 40.9 reading in October, the biggest monthly gain since April 2003, figures from the New York-based private research group showed today. The gauge, at a four-month high, exceeded the most-optimistic forecast in a Bloomberg News survey of economists.

Rising sentiment may help sustain sales during the holiday shopping season, which accounts for as much as 40 percent of retailers’ annual revenue. Fewer new claims for jobless benefits and cheaper fuel costs are easing the burden for American consumers, whose spending accounts for about 70 percent of the economy.

“Fundamentals for confidence are improving,” Ryan Sweet, a senior economist at Moody’s Analytics Inc. in West Chester, Pennsylvania, said before the report. “The labor market is healing, inflation is moderating and fears of a second recession have faded somewhat.”