Constant Approximation for Private Interdependent Valuations

TL;DR

This paper proves that in auction models with interdependent valuations and private signals, it is possible to achieve a constant approximation to the optimal social welfare, extending previous results that only applied to public signals.

Contribution

The paper establishes a constant factor approximation for interdependent valuations with private signals, resolving an open question from prior work by Eden et al. (2022).

Findings

Constant approximation for private interdependent valuations.

Extends SOS valuation results to private signals and valuations.

Settles open question on approximation bounds in this setting.

Abstract

The celebrated model of auctions with interdependent valuations, introduced by Milgrom and Weber in 1982, has been studied almost exclusively under private signals $s_1, \ldots, s_n$ of the $n$ bidders and public valuation functions $v_i(s_1, \ldots, s_n)$. Recent work in TCS has shown that this setting admits a constant approximation to the optimal social welfare if the valuations satisfy a natural property called submodularity over signals (SOS). More recently, Eden et al. (2022) have extended the analysis of interdependent valuations to include settings with private signals and private valuations, and established $O(\log^2 n)$-approximation for SOS valuations. In this paper we show that this setting admits a constant factor approximation, settling the open question raised by Eden et al. (2022).