A statistical study of a large chess games' database might shed some light on what a typical percentage of chess games are drawn due to the longstanding 3-fold repetition of position rule (resulting in a drawn result). The trouble is, quite a few of those chess games might have later ended in a draw, anyway, such as by the 50-move draw rule of chess, or simply by the players involved agreeing to a draw, or there being insufficient material on the board for either side to conceivably deliver a checkmate, perhaps far into the endgame stage in some cases.

However, something to consider is that draws by repetition being forbidden (normally/altogether? - not quite sure which, without my checking) being a part of the basic rules of Chinese Chess may hint that that sort of evidence-based 'study' just might have been carried out long ago, at least to some extent, in the case of that particular CV.

In the case of (now longtime standard 9x9) shogi, initiating that sort of 'study' may have occurred to that CV's own theoreticians, also, but, on the other hand, it may have been deemed unnecessary to make such (a study and/or rule) long ago, due to a high frequency of decisive results, rather than of draws, possibly being readily observed in a relatively modest sample size of finished games that were played between even highly skilled players, back then.

It's funny, though, that I had one shogi game offline, that I played against the friend who had introduced me to that CV, end in a draw by repetition result relatively early in the move count (even) from that CV's setup position - it's all the more funny because (I'm guessing) we had played far less than 150 games of that CV, in total, against each other.

Naturally, various attempts have been proposed to try to decrease the number of drawn results in chess games by (only slightly?!) modifying the basic rules of chess, such as to award 3/4 of a point for stalemating an opponent, or perhaps even for baring an opponent's K - any such attempts have yet to gain much traction, as far as I know (unless in the case of such things that are possibly viewed as a bit more 'radical', like 'chess without castling being allowed' [at the moment I forget the exact name of that proposal, which has had some testing, in high level events, at the least, in recent year{s}] are included, perhaps).

In my own case, as an aspiring CV inventor, I proposed, on a Canadian chess message board, long ago (then later had published here, on CVP site) what I thought was a quite/(perhaps too?) 'modest' departure from the rules of chess, to be used in a CV of mine I called 'Throne Chess'. That's where, if one player gets to legally move their own K to their opponent's K's starting square in the identical setup as for (FIDE) chess, they then win the game immediately, as an extra winning condition added to the basic rules of chess.

After I had first proposed 'Throne Chess', long ago, I noticed elsewhere, online, a couple of hundred of games (of that CV idea of mine) were play-tested, quite soon after I had first proposed that CV idea, and there was a reported increase of decisive results of 2%, over what would normally be expected for such a database sample size of finished (FIDE) chess games. Such a reported increase of only 2% more decisive games than what would be expected for a similar size database of (FIDE) chess games played is somewhat disappointing to me, and, in any event, this CV of mine, if played and studied more extensively, would I assume alter the expected result of any number of (perhaps) 'basic' chess endgames, if there is sufficiently adequate play, in terms of skill-level, by each side - something to consider for who knows how many 'modest' ways that may be proposed to tinker with the basic rules of (FIDE) chess.

A similar sort of (i.e. possibly unwelcome/unexpected) 'blowback' for aspiring CV inventors wishing to try to only 'modestly' tinker with the basic (FIDE) chess rules can happen even right in some otherwise quite standard chess opening variations, that have long been deemed perfectly acceptable to practical/professional chess players, perhaps most commonly if when preparing their opening repertoire with the Black army side, at home (such as, depending on if considering the rather commonplace case of if a decisive result is not strictly needed, in a given chess game that they might ever play, later on).

That, at least sometimes, might well include chess opening variations that have well-known draws by repetition that may even be otherwise unavoidable (e.g. if White wishes to indicate his possible willingness to go towards taking such a drawn result, maybe just for the sake of sometimes even letting Black be concerned about whether to avoid such a possible result), perhaps even lest an otherwise quite playable chess opening variation is cruelly pruned, e.g. due to having such a variation otherwise result in an outright loss for Black, due to there being draws by repetition ruled out if such a change to the basic rules of chess were to be made to that effect.