But are not ratings basically an expression of how well a horse ran?

Say the horse wasn't a late scratching, but ran second beaten 5 lengths. Your ratings method then says, OK he went one length worse than the previous week. Then, the winner weighs in light. He would now rate 4 lengths better using that logic than he did the previous week. This is the stumbling point - surely he rated the same whether the jockeyweighed in light or not, because his run did not get any better, he just got promoted a position.

Can you see where I am going here? Essentially, I think ratings are an expression of how well a given horse ran on a given day. How can his run have gotten better by five lengths ten minutes after he completed it, b/c a jockey weighed in light? He ran how he ran surely, and the rating should be the same either way, and if this is true, him therefore winning in the same grade that he ran 6th beaten 4 lengths in the previous week cannot be a length worse.

I hope this all doesn't sound annoying or petty or whatever, I actually consider the ramifications of this to be very important in terms of ratings.

Duritz