The Sensex at the Bombay Stock Exchange declined 72 points, or 0.4 percent, to close at 20,823 after volatile trade, amid falling regional markets, today. The Nifty at the National Stock Exchange fell 28 points, or 0.5 percent, to 6,187.Stock markets in Japan, China, Hong Kong, South Korea and Singapore lost between 0.1 percent and 0.8 percent.