The chess data is just there for reference, to see what kind of chess rating matches what kind of go strength

Furthermore, all the graphs top out at exactly the same point, which is the right side of the graph, at "top", just to the right of 99.9%

Also, all the graphs start out at exactly the same point, which is the left side of the graph, at 10%.

Also, saying that "the lower possible rated chess player, is stronger than experienced Go players" is meaningless in this context, stronger has no meaning when comparing players of different games, only when comparing players of the same game.

I have written a lot of text explaining the graph at Wikipedia's rank & ratings talk page, so read that for more on this.

One just needs to understand what it's saying; it's answering the question, "What do you call someone in the Xth percentile in the different systems?" Since the USCF and EGF give answers in the same "units" it seems perfectly fine to match them up even though the units mean different things in the different scales.

If anything, the part about it that's misleading is that the 5%, 95%, and following columns are spaced the same as the columns that are 10% apart. This gives the shape of the tails of the graph an unnatural shape.

The graph clearly shows the distribution of ratings as percentile. A useful way of presenting the data. Perhaps there would not be a discussion if there were four graphs, one of AGA, one for EGF, one for KGS and one for USCF.

What appears confusing to me is that 100 points EGF and 100 point USCF (which now uses Glicko rating in place of Elo rating system) appear to be equivalent to 20k because they are at the same location vertically on the graph...people may be mislead to think that its a nomogram they are viewing.

Herman, is it meant to be a nomogram ?

Please recognize that the graph presents a distribution of ratings in four systems, each of which tries to assign a numeric value to a changing characteristic of an individual based upon a very sparse sampling of that individuals performance against a small number of other individuals. As such, it is quite hard not to read too much into the data. But Arpad Elo is a good bit more eloquent that I

Often people who are not familiar with the nature and limitations of statistical methods tend to expect too much of the rating system. Ratings provide merely a comparison of performances, no more and no less. The measurement of the performance of an individual is always made relative to the performance of his competitors and both the performance of the player and of his opponents are subject to much the same random fluctutations. The measurement of the rating of an individual might well be compared with the measurement of the position of a cork bobbing up and down on the surface of agitated water with a yard stick tied to a rope and which is swaying in the wind.

I think it would be clearer if the diagram would have the percentile axis oriented vertically. Because after all, the percentile is supposed to be the "real" measure of skill level (the word "level" itself suggests a vertical orientation).

Then I can look up the skill level associated with a 2700 AGA rating or a 2200 USCF rating.