Reputation system are now everywhere. I was googling a bit on an artist I like and I stumbled across the curve reproduced below. They state that

The Artfacts.Net Artist Ranking is for information purposes only, and is not intended for trading purposes. The electronic chart is based on the data currently available to Artfacts.Net and should be only viewed as an aid to understand an artist's exhibition career in relation to the other artists stored in the Artfacts.Net Ranking System.