7 research outputs found
Improved Revenue Bounds for Posted-Price and Second-Price Mechanisms
We study revenue maximization through sequential posted-price (SPP)
mechanisms in single-dimensional settings with buyers and independent but
not necessarily identical value distributions. We construct the SPP mechanisms
by considering the best of two simple pricing rules: one that imitates the
revenue optimal mchanism, namely the Myersonian mechanism, via the taxation
principle and the other that posts a uniform price. Our pricing rules are
rather generalizable and yield the first improvement over long-established
approximation factors in several settings. We design factor-revealing
mathematical programs that crisply capture the approximation factor of our SPP
mechanism. In the single-unit setting, our SPP mechanism yields a better
approximation factor than the state of the art prior to our work (Azar,
Chiplunkar & Kaplan, 2018). In the multi-unit setting, our SPP mechanism yields
the first improved approximation factor over the state of the art after over
nine years (Yan, 2011 and Chakraborty et al., 2010). Our results on SPP
mechanisms immediately imply improved performance guarantees for the equivalent
free-order prophet inequality problem. In the position auction setting, our SPP
mechanism yields the first higher-than approximation factor. In eager
second-price (ESP) auctions, our two simple pricing rules lead to the first
improved approximation factor that is strictly greater than what is obtained by
the SPP mechanism in the single-unit setting.Comment: Accepted to Operations Researc
Sequential Posted Price Mechanisms with Correlated Valuations
We study the revenue performance of sequential posted price mechanisms and
some natural extensions, for a general setting where the valuations of the
buyers are drawn from a correlated distribution. Sequential posted price
mechanisms are conceptually simple mechanisms that work by proposing a
take-it-or-leave-it offer to each buyer. We apply sequential posted price
mechanisms to single-parameter multi-unit settings in which each buyer demands
only one item and the mechanism can assign the service to at most k of the
buyers. For standard sequential posted price mechanisms, we prove that with the
valuation distribution having finite support, no sequential posted price
mechanism can extract a constant fraction of the optimal expected revenue, even
with unlimited supply. We extend this result to the the case of a continuous
valuation distribution when various standard assumptions hold simultaneously.
In fact, it turns out that the best fraction of the optimal revenue that is
extractable by a sequential posted price mechanism is proportional to ratio of
the highest and lowest possible valuation. We prove that for two simple
generalizations of these mechanisms, a better revenue performance can be
achieved: if the sequential posted price mechanism has for each buyer the
option of either proposing an offer or asking the buyer for its valuation, then
a Omega(1/max{1,d}) fraction of the optimal revenue can be extracted, where d
denotes the degree of dependence of the valuations, ranging from complete
independence (d=0) to arbitrary dependence (d=n-1). Moreover, when we
generalize the sequential posted price mechanisms further, such that the
mechanism has the ability to make a take-it-or-leave-it offer to the i-th buyer
that depends on the valuations of all buyers except i's, we prove that a
constant fraction (2-sqrt{e})/4~0.088 of the optimal revenue can be always be
extracted.Comment: 29 pages, To appear in WINE 201
Robust Revenue Maximization Under Minimal Statistical Information
We study the problem of multi-dimensional revenue maximization when selling
items to a buyer that has additive valuations for them, drawn from a
(possibly correlated) prior distribution. Unlike traditional Bayesian auction
design, we assume that the seller has a very restricted knowledge of this
prior: they only know the mean and an upper bound on the
standard deviation of each item's marginal distribution. Our goal is to design
mechanisms that achieve good revenue against an ideal optimal auction that has
full knowledge of the distribution in advance. Informally, our main
contribution is a tight quantification of the interplay between the dispersity
of the priors and the aforementioned robust approximation ratio. Furthermore,
this can be achieved by very simple selling mechanisms.
More precisely, we show that selling the items via separate price lotteries
achieves an approximation ratio where is
the maximum coefficient of variation across the items. If forced to restrict
ourselves to deterministic mechanisms, this guarantee degrades to .
Assuming independence of the item valuations, these ratios can be further
improved by pricing the full bundle. For the case of identical means and
variances, in particular, we get a guarantee of which converges
to optimality as the number of items grows large. We demonstrate the optimality
of the above mechanisms by providing matching lower bounds. Our tight analysis
for the deterministic case resolves an open gap from the work of Azar and
Micali [ITCS'13].
As a by-product, we also show how one can directly use our upper bounds to
improve and extend previous results related to the parametric auctions of Azar
et al. [SODA'13]
Approximate revenue maximization in interdependent value settings
We study revenue maximization in settings where agents’ values are interdependent: each agent receives a signal drawn from a correlated distribution and agents’ values are functions of all of the signals. We introduce a variant of the generalized VCG auction with reserve prices and random admission, and show that this auction gives a constant approximation to the optimal expected revenue in matroid environments. Our results do not require any assumptions on the signal distributions, however, they require the value functions to satisfy a standard single-crossing property and a concavity-type condition