Statistical ranking systems place Capablanca high among the greatest players of all time. Nathan Divinsky and Raymond Keene's book "Warriors of the Mind" (1989) ranks him fifth, behind Garry Kasparov, Anatoly Karpov, Bobby Fischer and Mikhail Botvinnik—and immediately ahead of Emanuel Lasker. In his 1978 book "The Rating of Chessplayers, Past and Present", Arpad Elo gave retrospective ratings to players based on their performance over the best five-year span of their career. He concluded that Capablanca was the strongest of those surveyed, with Lasker and Botvinnik sharing second place. Chessmetrics (2005) is rather sensitive to the length of the periods being compared, and ranks Capablanca between third and fourth strongest of all time for peak periods ranging in length from one to 15 years. Its author, the statistician Jeff Sonas, concluded that Capablanca had more years in the top three than anyone except Lasker, Karpov and Kasparov—though Alekhine had more years in the top two positions. A 2006 study found that Capablanca was the most accurate of all the World Champions when compared with computer analysis of World Championship match games, but this analysis was criticized for using a second-rank chess program, "Crafty", modified to limit its calculations to six moves by each side, and for favoring players whose style matched that of the program. A 2011 computer analysis by Bratko and Guid using Rybka 2 and Rybka 3 found similar results to the 2006 Crafty analysis for Capablanca.