US stocks are slipping in afternoon trading Wednesday as Wall Street closes out a banner year for markets driven by both optimism and uncertainty.The S&P 500 was down 0.2 per cent. The Dow Jones Industrial Average fell 100 points, or 0.2 per cent, as of 1:47 p.m. Eastern time. The Nasdaq composite fell 0.1 per cent. The stock indexes are coming off a three-day losing streak.Trading is expected to be light ahead of the New Year’s Day holiday, when markets will be closed. With just one trading day left before ...