A mechanism can be simplified by restricting its message space. If the restricted message spaces satisfy a certain "outcome closure property," then the simplification is "tight": for every [epsilon][greater-or-equal, slanted]0, any [epsilon]-Nash equilibrium of the simplified mechanism is also...

We explore the performance of multi-round, price-guided combinatorial auctions for a previously untested class of value profiles in which synergies arise from shared fixed costs. We find that, in many cases, a simulator that bids straightforwardly does well in predicting auction performance, but...