However it is worked out, it is does produce some pretty good results. Whatever formula they use, it's been fine-tuned fairly well- I've never looked at a rating and been bemused when comparing to their actual performances.
Whether or not there is much value in a peak rating is a different question considering how heavily they favour recent performances, but it's a different question.
Whether or not there is much value in a peak rating is a different question considering how heavily they favour recent performances, but it's a different question.