The Sensex at the Bombay Stock Exchange gained a modest 28 points, to close at 21,171, on the last day of 2013, today.During the year, the Sensex had climbed nearly 9 per cent. The Nifty at the National Stock Exchange rose 13 points, to 6,304. For the full year, the Nifty gained 6.8 per cent.Stock markets in China, Hong Kong and Singapore advanced between 0.3 percent and 0.9 percent.