Prices for fine art during the past decade seemed to move in only one direction: up, up, up. But with real estate values sagging and stock markets slumping, prices for paintings are starting to stumble too. In auctions last week at Sotheby's and Christie's in New York City, artworks on the block sold for a total just under $100 million, or about 40% below expectations. An estimated one-third of the pieces went unsold. Among the jilted paintings: Willem de Kooning's Woman as Landscape, which was expected to fetch as much as $12 million.
A prime reason for the disappointment was that...