Is chess a game of skill or chance? To what extent? I want to know whether chess is a game of skill or game of chance, and how much is the degree of skill or chance in terms of percentage.

Edit (21 Feb 2014):

Please make sure that your answer includes credible references. To be sure that chess is a game of skill (or chance?).
If we remove the component of flawed, human players from the equation and consider just the game of chess itself as it is spelled out by the rules, then chess is purely a game of skill with no room for chance. That is, it is in principle possible for there to be a perfect chess player that plays optimally against every possible move sequence by an opponent, and that perfect player would never falter due to chance or luck. Such perfect players already exist at the level of chess positions with only a handful of pieces: endgame tablebases consist of all the information necessary for perfect play in those positions, and if you play from such a position against an opponent with access to those tablebases, chance can play no role in stopping them from getting their deserved result.

However, the problem of computing a tablebase for the starting position of chess, with its 32 pieces, is far, far from tractable. So while optimal play does exist for all positions in chess, nobody knows for sure what optimal play is for the vast, vast majority of positions. Looked at in that light, when two humans (or even strong chess engines) play a game against one another, something that can reasonably be viewed as chance (for one side at least) can definitely play a role, but for what I have in mind at least, the root cause of any outcome is still skill (or its temporary absence).

Here's an example of what I mean. In the recent Zurich Chess Challenge, Nakamura was playing a fine game against Carlsen, to the point where he had an overwhelming, winning advantage. At that point, it could safely be said that Carlsen "deserved" to lose.

[fen "4r1k1/1p3pPp/6q1/2pPpNP1/p1n1P3/P6Q/7R/K7 w KQkq - 0 1"]
[White "Nakamura, Hikaru"]
[Black "Carlsen, Magnus"]
[Event "Zurich Chess Challenge"]
[Result "0-1"]

1.d6? (1.Qf1!)


But Nakamura made a crucial mistake that let Carlsen off the hook, later followed by further poor play that even allowed Carlsen to win. If someone were to say, "Carlsen was lucky to win that day," I'd say there's truth to that. (Carlsen certainly deserves credit for defending in such a way that Nakamura could still go wrong, but even so, he was fortunate that Nakamura erred as he did.) But the luck from Carlsen's side originated from nothing more than a momentary lack of skill on Nakamura's part. Finding the right move was entirely within Nakamura's power, but he wasn't quite skillful enough to find it in that moment.

As in most human endeavors, there is some element of chance in the competitive results of chess games. But that luck for one side generally comes in the form of what kind of lack of skill one's opponent shows (and when).