Those of you relying on Betfair for getting a bet on may well carry out Betfair based data analysis and usually this means analysing data to Betfair SP. In my case and probably yours its not because you intend to bet to BSP but it does hopefully give you an indication of what price you could have hoped for just before the off.
I had not questioned the integrity of BSP until today when I discovered that around 40% of handicap races go off underbroke to BSP. The market is anywhere from 96% to 100% in around 40% of cases. At first I thought that late withdrawels might not be reflected in the BSP and to test this I looked at NH racing which probably has less late NR’s due to the fact that no stalls are involved. I found the same trend regardless of racing code. This is concerning as the gap between reality and BSP may well be wider than we first imagined. We have always assumed some degredation but that was on the assumption that BSP was around 100%.
I have contacted Betfair on this issue and will update when I hear something. In the meantime it does not mean that all BSP based research should go in the bin but it does mean allow for some slack when reality hits. Then again that kind of advice should be applied to any historical research you conduct. Past returns do not gaurantee etc etc etc