I will use the touring plans crowd calendars as a guide, since they have so much research and data behind their calculations. They can't be perfect all the time, because there are always factors out of their control - weather, rides being down, etc. But they are darned close with the vast majority of their predictions, and they post on their crowd calendar how accurate they were on the day before. It's pretty impressive. I don't have any idea what methods other sites use, and I'm not putting them down. I just like that I know what Touring Plans' methodology is and that it isn't just guesses or repeats from last year.