Glen,

Agreed liquidity is low and would be a problem. I am not sure on how your filter works but I will assume matched is the same as traded as per the betfair summary for each horse. In that case matched is the bet amount not the liabilitya dn instead of 5000 you would want $5 - $10. It would be rare for any 50/1 shot having more then $50 matched as that is a liability of $2500.

More importantly though, I wrote this as a response to some articles I have read on the bias ad was hoping someone could back up my claims with their own figures. I am glad though that your figures support the bias. Means it does exist and academics are blinded by what they want to see.