Falling for the third straight session, the Sensex at the Bombay Stock Exchange plunged 432 points, or 2.1 percent, to 20,157, today, on poor industrial growth data, and weak global markets. The Nifty at the National Stock Exchange slid 123 points, or 2 percent, to 6,072.Stock markets in Japan, China, Hong Kong, and Singapore dropped between 1.3 percent and 5 percent.