One point to note is that the normal way to get impact values is to group different factors together as "all in". Take distance for instance, 1200M at one race track is vastly different to 1200M at another. The position of the first turn or the length of straight makes a different style of race.
Similarly a 7 horse race is vastly different to a 15 horse race.
So you must group like with like which may not give enough races to make a true sample.
If you put 15 pots of paint together, you will get absolute rubbish. However if you mix them by base colour in three groups, you may end up with three reasonable colours.

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"God made man in his image". He then went to great lengths to ensure that each and every person was unique. God then pondered and said "I will call these human, as very few will rise from the herd to be called individual" http://www.propun.com.au/racing_for...ttons/quote.gif