Economic confidence among U.S. small-business owners declined in December for the fifth consecutive month, according to Discover.

Of 1,000 owners surveyed nationwide, only 28 percent said they felt that economic conditions for their businesses were improving, the report said. Overall, the index dropped to 92.7, down from 93.2 in November and 109.7 at the same time a year ago.

"The mood remains cautious as fewer small business owners feel like economic conditions for their businesses are getting better," Sastry Rachakonda, the director of Discover's business credit card, said in a statement.