Not every database. I take t into account in my database. Its not hard to calculate as you know the number of winning positions which betfair is paying out and if you find more winners then the expeced number then you modify the figures using their calc. It is the same with scratchings after prices are recorded. You need a "seen" price and a "final" price. It doesn't make too much of a difference but it can be enough to swing some marginal systems.