The National Federation of Independent Business (NFIB) released its small-business optimism index for the U.S. on Tuesday. The index dropped to 92.9 in February from 93.9 in January. It was the lowest level since February 2014.

6 of 10 sub-indexes declined last month, while 4 sub-indexes were flat.

"Monthly management of monetary policy using data subject to substantial revision is inconsistent with the acknowledged lags in policy and not supportive of real growth which requires more policy consistency. Financial markets of course thrive on the variability such policies produce and support a zero interest-rate policy," NFIB Chief Economist Bill Dunkelberg said.