The randomized communication complexity of revenue maximization

We study the communication complexity of incentive compatible auction-protocols between a monopolist seller and a single buyer with a combinatorial valuation function over n items [Rubinstein and Zhao 2021]. Motivated by the fact that revenue-optimal auctions are randomized [Thanassoulis 2004; Manelli and Vincent 2010; Briest et al. 2010; Pavlov 2011; Hart and Reny 2015] (as well as by an open problem of Babaioff, Gonczarowski, and Nisan [Babaioff et al. 2017]), we focus on the randomized communication complexity of this problem (in contrast to most prior work on deterministic communication). We design simple, incentive compatible, and revenue-optimal auction-protocols whose expected communication complexity is much (in fact infinitely) more efficient than their deterministic counterparts. We also give nearly matching lower bounds on the expected communication complexity of approximately-revenue-optimal auctions. These results follow from a simple characterization of incentive compatible auction-protocols that allows us to prove lower bounds against randomized auction-protocols. In particular, our lower bounds give the first approximation-resistant, exponential separation between communication complexity of incentivizing vs implementing a Bayesian incentive compatible social choice rule, settling an open question of Fadel and Segal [Fadel and Segal 2009].

Editors' introduction

This issue of SIGecom Exchanges brings to our readers a letter from the SIGecom executive committee, the job candidate profiles for 2022, two surveys, and three research letters.

Network structure and social learning

We describe results from Dasaratha and He [DH21a] and Dasaratha and He [DH20] about how network structure influences social learning outcomes. These papers share a tractable sequential model that lets us compare learning dynamics across networks. With Bayesian agents, incomplete networks can generate informational confounding that makes learning arbitrarily inefficient. With naive agents, related forces can lead to mislearning.

Constraints in fair division

The fair allocation of resources to interested agents is a fundamental problem in society. While the majority of the fair division literature assumes that all allocations are feasible, in practice there are often constraints on the allocation that can be chosen. In this survey, we discuss fairness guarantees for both divisible (cake cutting) and indivisible resources under several common types of constraints, including connectivity, cardinality, matroid, geometric, separation, budget, and conflict constraints. We also outline a number of open questions and directions.

Letter from SIGecom executive committee

Despite the challenges of the past year, the SIGecom community has continued to grow, and to embrace opportunities to gather and connect (virtually).

Market design job market candidate profiles 2022

Inspired by the SIGecom Exchanges' annual survey of job market candidates, 1 this is the second annual collection of profiles of the junior faculty job market candidates of the market design community. The nine candidates are listed alphabetically. Along with information regarding the candidate's bio, job market paper, other representative papers, and short research summary, each profile also contains links to the candidate's homepage and CV.

SIGecom job market candidate profiles 2022

This is the seventh annual collection of profiles of the junior faculty job market candidates of the SIGecom community. The twenty four candidates for 2022 are listed alphabetically and indexed by research areas that define the interests of the community. The candidates can be contacted individually or via the moderated mailing list [email protected].

Exploiting social media for fake reviews

We provide an overview of our recent work that studies the market for fake product reviews on Amazon.com where reviews are purchased in large private internet groups on Facebook and other sites. We find that a wide array of products purchase fake reviews, including products with many reviews and high average ratings. Buying fake reviews on Facebook is associated with a significant but short-term increase in average rating and number of reviews. We exploit a sharp but temporary policy shift by Amazon to show that rating manipulation has a large causal effect on sales. Finally, we examine whether rating manipulation harms consumers or whether it is mostly used by high-quality or young products in a manner akin to advertising. We find that after firms stop buying fake reviews, their average ratings fall and the share of one-star reviews increases significantly, particularly for young products, indicating rating manipulation is mostly used by low-quality products and is deceiving and harming consumers.

Exchange markets

The exchange market is a basic model of an economy, where agents bring resources that they own to the market in order to exchange them for other goods that they need. There is a rich literature on the equilibrium properties of such markets starting with the work of Arrow and Debreu. In this note we survey recent results on proportional response dynamics in exchange markets with linear utilities and suggest several directions for future work.

Economies with complex property rights

We discuss the exclusion core, a solution concept for object-allocation and object-exchange problems. The exclusion core is based on the right of exclusion and is especially useful for the analysis of economies with complicated property arrangements, such as those with shared ownership. The exclusion core coincides with the (strong) core in classic settings, and is closely related to the celebrated Top Trading Cycles algorithm.