Useful discussion in this thread. My two cents:

I've given up on entirely mechanical systems. I see all "systems" as selection tools and nothing more. I look for systems that throw up a good volume of selections and then I consider the selections in the context of each particular race.

The best "system" is the sound judgement that comes from watching lots and lots and lots of races and learning the races to stay out of and learning what is a good bet and what is not. Nothing can replace that. You must, in my opinion, consider the *context of the race* - purely mechanical systems will fail or draw back to break even.

There are inherent problems in and limitations to predicting the future from the past. The basic problem is that every race - every race! - is a totally unique event. There has never, ever been a race like it before and never will be again. Every Melbourne Cup is a totally unique event, regardless of the family resemblances between all the unique events labelled "Melbourne Cup".

This is why systems should be tested on live races and why, even then, judgement is necessary. It is also why testing a system on 20,000 races may be meaningless - because we are not betting on 20,000 races but on this particular race, and it is a unique event with unique factors.

Often my major system will indicate a good selection but I look at the race and think better of it. I'm getting better at this, I reckon. Same with the commercial system I purchased once. Look at the race. Nice selection, but no.

As for why systems prosper and then collapse as if they were shareware and expired after 28 days, I don't know, but it is an observable thing. I have no idea. Pluto going retrograde in Sagittarius?

But it doesn't happen to all systems. I pulled a little money-spinner from the drawer the other day and dusted it off. Two years ago it was running at a small profit before I got bored. Checking recent weeks, it's still making money. Not much, but consistent. No change in the strike pattern.

What factors make for a consistent system? What factors are eratic long term?

Cheers

Hermes