As a longtime follower of PPM’s Class and Assessments horses, I was delighted when Emission scored recently at 50/1 in the BTC Sprint at Doomben.

As no doubt many PPM readers will know, Emission was THE selection for the race in The Optimist's Class and Assessments. Yes, clear as a bell, Emission was the one to back. What a winner. It's not often they come along so clearly sign-posted for us loyal fans of the C & A's.

So what are they all about, and how does The Optimist work such miracles, and what about ratings generally? We hear so much about them, but what are they really worth to a punter, and can the punter prepare his or her own ratings and be successful?

I'll be exploring these themes in a series of articles in PPM, and I trust we will all be a little wiser at the end of them. Firstly, though, to The Optimist.

He tells me: "My assessments have always been my own, and I make no excuses for their being subjective. I try to consider the likelihood of horses striking form, or going out of it, in the lifetime of the magazine, in Sydney and Melbourne.

"My basic figure is 60, although this has varied between about 57 and 62 over the years. A really good rating for a 4yo-plus is 64 or 65; a top rating around the high 60s, and anything that gets to 70 is quite exceptional.

"Three-year-olds do not appear until around November, and a potentially very good one will get 60 or even 61. They will be in the mid-60s by the end of the season if they are (in my view) top-class.

"Distances are winning distances. I played with these for years and found that demanding that the horse had done it worked as well as anything.

"Track conditions are for the readers' guidance and whilst I do not use them in the results, I certainly regard them as very important. For example, note how partial County Tyrone is to a wet track, as evidenced by his fine run in the O'Shea Stakes.

"Many double-figure winners have been struck over the years, but if I was able to direct my readers' use of these arbitrary figures I would say: If a horse is assessed significantly above anything else in its field, and the distance is appropriate and the track conditions favourable, take note of it. Use the specialist papers to see when its wins over the distance were, and how it handles today's track.

"In other words, the C & A's are a guide, as they have now been, and stood the test of time, for exactly 30 years.

So there you have it from the man himself, the reasoning behind the Class and Assessments horses to follow that you find in PPM each issue.

Each punter has his or her own view about how to compile ratings. The skill involved will prove the measure of the worth of anyone's ratings figures.

Most race ratings approaches operate on the basis of a universal handicap, in which every horse's ability is expressed numerically, usually in kilos weight.

Typically, the basic rating is adjusted to bring it in line with the weights allotted according to the conditions of the race in which the horse is entered. This gives the user a means of rapidly assessing a particular race.

Thus a horse with an adjusted rating of, say, 60 is 1.5kg "better in" than one with a rating of 58.5. This in turn means that, in theory, the horse rated 60 should finish about a length in front of a horse rated 58.5, depending on the distance of the race.

The words "in theory" are crucial here, because if handicap ratings always worked out, bookmakers would cease to exist, as would betting.

The best horse on form would always win. In practice, life is not so simple. In non-handicap races, only about 40 per cent of top-rated horses win, while in handicaps the figure is about 20 per cent, depending on the ratings used.

A f