The National Federation of Independent Business (NFIB) released its small-business optimism index for the U.S. on Tuesday. The index dropped to 93.9 in January from 95.2 in December.

3 of 10 sub-indexes rose last month, 6 sub-indexes fell, while one sub-index was flat.

"The Small Business Optimism Index fell a bit more than one point, not much of a response to stock market turbulence or the Federal Reserve's move to raise interest rates. The decline in optimism was accounted for by two important Index components, expected business conditions in six months and expected real sales," NFIB Chief Economist Bill Dunkelberg said.