Falling for the second straight day, the Sensex at the Bombay Stock Exchange dropped 163 points, or 0.9 percent, to close at 18,684, amid declining global markets, today. The Nifty at the National Stock Exchange fell 53 points, or 0.9 percent, to 5,686.Stock markets in Japan, China, Hong Kong, South Korea and Singapore slipped between 0.1 percent and 1 percent.