U.S. small-business confidence and hiring plans increased in May to their highest levels of the year, but the looming U.S. presidential election also drove uncertainty to nearly a four-year high, a survey showed on Tuesday. The National Federation of Independent Business (NFIB) said its Small Business Optimism Index rose eight-tenths of a point to 90.5 last month, the second consecutive month it has risen after slumping in March to the lowest level since December 2012. Despite the...