A very interesting article using computer analysis to gauge how error free and how complex the position of several players from history:
http://www.chessbase.com/Home/TabId...quality-of-play-at-the-candidates-080413.aspx
Interestingly Ivanchuk has the second highest complexity of all the players, which may be why he loses on time so often!
The obvious thing to do that the authors don't do is to normalize the error number by the complexity measure. This would then give a better indication of the quality of moves. By this measure, I would not be surprised to see Carlsen, Kasparov and Fischer at the top. Here is the result of that compuation for the candidates 2013:
So Carlsen is 21.16 / 3.86 = 5.48, etc.
Carlsen 5.48
Grischuck 4.94
Aronian 4.20
Kramnik 3.92
IvanChuck 3.27
Gelfand 2.97
Svidler 2.89
Radjabov 2.33
In fact, other than Grischuck, this follows the pattern of strongest player. So, if you are looking for a player to improve dramatically soon, it would be Grischuck. And one that was and may still be way overrated is Radjabov.
Svidler in an interview did not understand why he only scored the way he did. Increase the complexity of your games while keeping the number of errors more or less stable, and you will score much higher. The logic is obvious, the more pressure you put on a player, the more errors he makes.
Note that if you are able to extrapolate Anand's results, it would be:
Anand 4.18.
That means he stands almost no chance againt Carlsen in the WC, unless he gets his error term down or increases his complexity considerably.