Sotheby's third-quarter loss widened as the art auction house posted a worst-than-expected decline in revenue and a tax expense.

Auction houses have been struggling to secure enough top materials to entice bidders, as the economic downturn is forcing them to rely heavily on individuals to sell art for personal reasons. The company's business is highly cyclical, according to Moody's Ratings Services, which said it expects Sotheby's to weather the current downturn while maintaining good liquidity.