It doesn't seem to work in a one to one way though. I vaguely remember that soon after I joined my rating was 10, but then it plummeted to something like 7.5 for no reason I could see. It then climbed back up to 9.9 and stays around there depending mostly whether Faith is in one of her moods or not.
Can you describe how it works, just for interest.
If it only factors in the last 90 days, then it makes sense that the rating can fluctuate without having received any recent cheers/jeers—as past ratings slowly fall out of the calculation whether they are negative or positive they will positively or negatively (respectively) affect the 90-day rating.