A method and system conduct an auction for advertising across multiple markets. A first market conducts a first auction for a first advertising impression. A first bid is selected as the auction winner and a ratio is computed as the first bid plus a spread to the second highest bid. The price to be paid is the lower of the first bid or the first bid multiplied by the ratio. The first bid, second bid, and spread are transmitted to a second market for a second advertising impression auction. The second market respects the rules of the first market's auction where such that if the first bid is selected as the winner, a ratio is computed as the first bid plus the spread to the next highest bid. The price to be paid for the second impression is the first bid multiplied by the new ratio.