Short pieces written while building the game. They explain the rules we play by and a few things we learned about the numbers.
What "including the buyer's premium" means
When a painting is knocked down at auction, the number the auctioneer says is the hammer price. The buyer then pays the auction house a fee on top, the buyer's premium, which at the big houses runs from roughly 15 to 27 percent depending on the price band. The figure reported in the press, and the one on a Christie's or Sotheby's results page, is almost always hammer plus premium.
GTP of Art shows the premium-inclusive figure whenever the source gives it, and says "incl. fees" on the reveal. When a source only reports the hammer price, the reveal says "hammer". We never mix the two inside one question: in "Which is pricier?" both works are compared on the same basis.
Private sales are different again. There is no public record, only a report, often from a single source. The app marks those as "reported", and you should treat them as approximate.
Why every price says "approx."
A sale in London is priced in pounds. To compare it with a sale in New York, we convert at the exchange rate of the sale date, so a 1990 price in pounds becomes a 1990 price in dollars. That is already an approximation. Then there is inflation: a work that sold for two million dollars in 1961 cost, in purchasing power, far more than a work that sells for two million today. The info sheet on each reveal shows an inflation-adjusted estimate using the US consumer price index, and "Which is pricier?" compares works in today's dollars for that reason.
The game rounds every price to two significant figures. A sale of $82,500,000 appears as $83M. The point is not the last digit; it is the order of magnitude, and whether your eye can tell a fifty-thousand-dollar picture from a five-million-dollar one.
Where the pictures come from, and why there is no Warhol
All 417 works in the game are in the public domain: the artist died more than seventy years ago and the work was published before 1931. That is what lets us bundle the images with the app, offline, at no cost to you. Museums such as The Met, the Art Institute of Chicago, the Cleveland Museum of Art and the Rijksmuseum release photographs of their public-domain works for any use; Wikimedia Commons hosts faithful reproductions of many more.
It also explains what is missing. Picasso, Rothko, Warhol and Basquiat account for many of the biggest auction headlines, but their work is still in copyright, and we will not show it without a licence. For prints, posters and photographs, the museum's sheet is usually not the exact sheet that sold, only another impression of the same edition; the app says so on the reveal.
Living artists are a different story, and one we are working on: a future version will add contemporary works offered for sale by artists and marketplaces, with the asking price as the answer and a link to the listing if you like what you see.
