A New Payment Rule for Core-Selecting Package Auctions

We propose a new, easy-to-implement, class of payment rules, "Reference Rules", to make core-selecting package auctions more robust.  Small, almost-riskless, profitable deviations from "truthful bidding" are often easy for bidders to find under currently-used payment rules.  Reference Rules perform better than existing rules on our marginal-incentive-to-deviate criterion, and are as robust as existing rules to large deviations.  Other considerations, including fairness and comprehensibility, also support the use of Reference Rules.