Abstract: A computing system can include an advertisement server that, as part of an auction for a paid search advertisement, calculates an original score for a particular bidder by using a scoring function; calculates an optimized score for the particular bidder by obtaining a score estimate from a system storing results of an offline historical model for the particular bidder, calculating a reserve price value by calculating ?(s*-?i), and adding the reserve price value (which may be a negative value) to the original score; and assigns the particular bidder to a paid search advertisement slot according to the optimized score. The optimized score can be represented by the formula {tilde over (s)}i=si+?(s*??i), where si is the original score, ? is a multiplier between 0 and 1, s* is a fixed point that may be equal to 0, and ?i is the score estimate for the bidder that comes from the offline historical model.