Mumbai, June 11 -- Small business owners in U.S. grew more optimistic in May as they reported improvements in their expected business conditions and sales expectations, according to the National Federation of Independent Business (NFIB).

The NFIB Small Business Optimism Index increased by three points in May to 98.8, slightly above the 51-year average of 98.

Expected business conditions and sales expectations contributed the most to the rise in the index.

The Uncertainty Index rose two points from April to 94. Eighteen percent of small business owners reported taxes as their single most important problem, up two points from April and ranking as the top problem.

The share of business owners expecting better business conditions rose 10 pe...