Read back a page or so in this thread. It's not just about ranking, it's also the number of goods vs the number of bads. For example if you have 50 votes, all between 7 and 10 (avg of 8.9), compared to someone with three 9's and two 10's (avg of 9.3), the 8.9 might rank above the 9.3 because there's less variance in the voting. Most people vote it high, rather than just a few. This way a new car can't get one vote of 10 and be at the number 1 spot.