Some years ago, Bill Robertie assigned levels of complexity to different games (I believe checkers was

.
In order to be at level 3, for example, you needed to consistently score 75% against a level 2 player; to be at level 4, to consistently score 75% against a level 3 player etc...
I used a similar principle in Logical Checkers, Book 1, to conclude that there are 10 distinct levels in the game (actually Chinook and Tinsley registered was might be called 10+).
Level 1: Basic novice (90% of the population); Level 2: Advanced Novice (9% of the population); Levels 3-6: expert; Levels 7 and 8: master; levels 9 and 10: grandmaster.
The main point of contention in Robertie's thesis was, what constitutes the smallest 'unit of currency' in a given game? (Chess, checkers, backgammon ...) In 3-move checkers, the smallest possible unit is a 2-game heat. This would not render the 10 levels I describe. In my view, 4-game heats probably do this, 6-game heats almost certainly do and 8-game heats definitely do. (This is essentially just echoing the lively comments Willie Ryan made about the 1950 Us Nat Ty in
Big League Checkers where he argued strongly for 8-game heats over 4-game heats.) To give a concrete example: I'm confident that a super-grandmaster like Alex (middle of level 10) would register 75% against a run-of-the-mill one like myself at my peak (middle of level 9) assuming 8-game heats were played. That is, he would likely win 2 heats and draw 2 heats. (In fact, he would probably do better than this, perhaps winning all 4 heats, and might only require 4 or 6-game heats).
Whether or not it is reasonable to define one unit to be an 8-game heat is a moot point: I
think it is. However, given that ACF heats consist of 4 games, some might disagree.
Now, by extending one unit to represent a 16-game heat or even a 32-game heat, I believe the level of complexity could artificially be extended to 11 and 12 levels respectively. However, I think this is stretching a point and is not a reasonable model.