impact of commission?

[alun]

if you were researching a system and 100% return was break even ie the backer gets 100% of their money, what %age return would you need to look for in order to overcome the effect of a 5% betfair commission. Two answers required a) if backing b) if laying Al

[slapdash]

Re: impact of commission? If I understand the question correctly, it depends on the odds you're backing at. For example, if you are backing at odds of 10.0, then after 5% commission, the "real" odds you're getting are 9.55, so to break even after commission, you'd need 1 in 9.55 of your bets to win, and at that strike rate, your return before commission would be 100% times 10.0/9.55, wich is about 104.7%. But if you back at odds of 1.10, then your "real" odds after 5% commission are 1.095, so you need a strike rate of 1 in 1.095 to break even after commission, and at that strike rate your return before commission would be 100% times 1.10/1.095, which is about 100.46%. Basically, at large odds, you need nearly 105%, but as the odds get smaller so does the percentage return you need before commission. I hope the examples above make it clear how you'd work it out for other odds.