Picasso and Warhol were the most actively traded artists last year. “Picasso collectors raised $153.2 million last year from 1,409 works sold at auction, Artprice said. Owners of Warhols realized $86.7 million from 660 images, while 22 Monets took $61.5 million and 18 Canalettos $55.5 million, it said. Auction volumes are a guide to which works are becoming more liquid or expensive and which may be harder to buy and sell over time.”