Sotheby's, after trailing Christie's International in 2006, sold about $6 billion of art at auctions and in private transactions last year, drawing even with its rival. Sotheby's sold $5.33 billion of art at auctions, and arranged more than $668 million of private deals outside the public salerooms, said analyst George Sutton at Craig-Hallum Capital Group LLC of Minneapolis. That was a 46 percent increase from $3.66 billion a year earlier. Christie's estimated its art sales at about $6 billion last year. Sotheby's last overtook Christie's after it sold Pablo Picasso's "Garcon a la Pipe" for $104.2 million in 2004, then fell behind the next year, based on auction totals. As the art market boomed, Sotheby's promised minimum prices to sellers to win high-priced works by Francis Bacon and other contemporary artists. "They won a larger share of the key consignments in 2007," Sutton said in an e-mail. "As the balance sheet has improved, they have been able to offer more aggressive options for sellers, including guarantees and loans." Publicly traded Sotheby's, which is due to report fourth- quarter results next month, couldn't immediately provide a final total for 2007 auctions and private sales, said spokeswoman Diana Phillips. Christie's, which is owned by the French billionaire Francois Pinault, will give details of its transactions next week, said spokesman Toby Usnik. Christie's doesn't disclose revenue or profit, though it gives twice yearly reports on the value of art sold. More Private Deals "We and our shareholder are very pleased with Christie's impressive growth in 2007," which lifted totals to about $6 billion, Christie's Chief Executive Officer Ed Dolman said in an e-mail. "We aim to build on this success by continuing to provide our clients with the best quality works and service."Sotheby's and Christie's are stepping up their private transactions to augment revenue. Russian billionaire Alisher Usmanov said on Ekho Moskvy radio in September he paid more than 36 million pounds ($71 million) for Russian art collected by the late cellist Mstislav Rostropovich, which Sotheby's had planned to auction in London, then sold to him directly. Market Decline A prolonged decline in the world's stock markets or an unforeseen crisis could reduce the money available to buy art, experts said. Auction volumes, estimated at more than $10 billion last year, were at $3.4 billion in 2003, according to Moody's Investors Service, which rates Sotheby's debt. Sotheby's shares were at $37.64, off 94 cents, at 12.04 p.m. in New York Stock Exchange composite trading. The 52-week high of $61.40 was reached during the day on Oct. 11. After a Vincent van Gogh painting didn't sell on Nov. 7, Sotheby's plunged 35 percent over three days as it took a $14.6 million loss on guaranteed impressionist works that sold below their estimates. Sotheby's, with its main salerooms in New York, is incorporated in Wilmington, Delaware. Christie's is based in London.