Magnus Carlsen is the odds-on favorite to retain his title as World Chess Champion in a showdown this month against Sergey Karjakin.

Given how well the 25-year-old Norwegian is playing, that's no surprise.

Carlsen in the past year has played with an unmatched Computer Aggregated Precision Score of 98.54, a new measure from Chess.com that analyzes moves with computers. His scores over the past five years (98.38) and as an adult (98.32) have also not been matched.

Historical greats Gerry Kasparov and Bobby Fischer score 97.51 and 97.59, respectively.

Karjakin, a 26-year-old from Russia, rates 97.97 over his adult career—impressive, but well short of Carlsen.

Chess.com director of research Roland Walker noted that his team had not analyzed every player in history but said it seemed clear that Carlsen was the most accurate player ever.

In 19 matches between Carlsen and Karjakin, Karjakin has played unusually well, with a CAPS rating of 98.17 compared to Carlsen's 98.50. Carlsen won 4 of them, lost 1, and drew the rest.

The chess world typically compares players using Elo ratings, calculated by looking at a player's record and the relative strength of his or her opponents. One problem with those is that it's imprecise to compare scores in different eras. Another problem is that they can undervalue a player who is well ahead of the pack, as seems to be the case with the World Champion.

"Carlsen's Elo is substantially understated due to the lack of near-rival opponents," Walker wrote in an email.

Carlsen reached the highest Elo score in history of 2882 in 2014 (currently, he has a 2853); Kasparov has the next highest ever at 2851; Karjakin is a ways back at 2772. Based on CAPS analysis, however, Carlsen's score in the past year should be a stunning 3073.

International Chess Master Danny Rensch, Vice President of Chess.com, noted that CAPS wasn't a replacement for Elo but a useful complement. "Though we don't consider CAPS a true replacement for the 'head to head' rankings that Elo ratings have always offered for years, we do believe it can provide insight into our game of kings that has never been available before," he wrote in an email.

Carlsen showed an uncanny understanding of chess from a young age, as shown in the new documentary, "Magnus."

Carlsen told Business Insider in 2013 that he thought he could get a lot better.

After winning the World Chess Championship in 2013 and defending his title in 2014, Carlsen will face Karjakin in a best-of-12 match in New York from Nov. 11 to 30.