Grand National 2013 - The AR system

Hi,
I've slightly tweaked the successful system I used last year and compiled stats for this year's race.
The system is called the 'Avoidance Rating' (AR).
Firstly, don't expect this system to spit out a winner - the race is too unpredictable and there are too many variables.  It won't tell you what to bet on, but it will tell you which three-legged donkeys to avoid.
With such a huge field, the goal of this system is to help people who, quite frankly, don't have a clue where to start.  The aim is to narrow the field and cross-off up to two-thirds of the runners, allowing Mr Average to pick his bets from the remaining 10-15 horses - safe in the knowledge he shouldn't be wasting his money.
This system gives Joe Bloggs punter - who doesn't follow horse racing religiously - a chance to have a bet and (hopefully) have some excitement until the end of the race and win some money.
About the system
It uses 8 key stats from past Grand Nationals, plus 8 additional measures of my own taking into account both horse and jockey.
Each of these 16 facts then carry various weightings and produce an overall AR for each horse. 
The higher the AR, the more reasons there are to avoid it.

Last year's results (2012)

Last year the system worked very well.
Jargon:
Horses finishing in 1st-6th are referred to as 'placed'.
Horses falling, pulled up, or finishing worse than 6th are referred to as 'nowhere'.
Horses bought down by others are discounted from results.
I was immediately able to eliminate almost half the field (with an AR of >=1.75).
Of the 19 horses I eliminated, 18 of them ended up nowhere (95%).  The single exception was the 100/1 shot In Compliance which placed 5th.
At the other end of the scale, 21 horses had an AR of 1.50 or below.  After discounting 3 which were bought down, this leaves 18.  The remaining 5 places were filled with horses from this group of 18.  Sunninghill Boy, who came second in a photo finish, had an AR of just 0.50.
So, in terms of sorting the wheat from the chaff, the AR system worked very well.

This year's AR table

This is available in my next post - check it out!