Falling for the third straight session, the Sensex at the Bombay Stock Exchange dropped 59 points, or 0.3 percent, to close at 18,450, amid falling Asian and European markets, on Friday. The Nifty at the National Stock Exchange lost 22 points, or 0.4 percent, to 5,553.Stock markets in Hong Kong, South Korea and Singapore declined between 0.2 percent and 2.7 percent.