As I understand it, the GW scores we see are strictly rankings. Or really an average of how the GW raters rank courses in each category. They are not scores against an absolute scale. A comparison is how much money a pro golfer makes in any year, vs where he stands on the money winnings list. GW shows us where the courses stand. Not how much actual money they made.
GW takes all the courses in, say, the modern category. Raters end up giving each course they play a score from one to ten. While I don't have the numbers exact, a ten means the ranker considers that course one of the best 5 modern courses in the country. (Instead of 5, that number may be 3, or 10, but I don't think it's anything greater than that.) A nine means it ranks somewhere between 5 and 25 (or similar numbers). An 8 means it's between 26 and 75.
Again, I don't know the precise numbers. But I'm pretty sure they are close to the ones I cited.
Then GW averages all the scores from its raters. Maybe they smooth the numbers out with some statistical magic. From Jonathan's comment, sad to say, that seems likely. But the scores you see are that average, statistically massaged or not.
Which is why (if all this is correct!) Huck is right. When Sand Hills gets a 10, it only means that rater thinks Sand Hills is among the top 5 (or whatever) modern courses in the nation. The same rater may rank Sand Hills 100 among all courses. He may rank it first. We have no way of knowing from the numbers GW supplies us.
Andy Troeger: the state lists only compare public access courses. No private courses. And almost no public courses are among the top 100 classic. Only a few, by my quick count. So no real basis to compare.
Tim Bert, good question IMO. A few years ago I asked Brad Klein how they, as individual raters, average their raw scores. It was not a straight arithmetic average. They could weight the categories differently. And IIRC, each rater could decide how to weight the categories. So one rater might give routing a bigger weight. Another might give conditioning.
I would like to see those "raw" scores. Which are different from the scores we see in GW.