3,582 research outputs found
The Combinatorial World (of Auctions) According to GARP
Revealed preference techniques are used to test whether a data set is
compatible with rational behaviour. They are also incorporated as constraints
in mechanism design to encourage truthful behaviour in applications such as
combinatorial auctions. In the auction setting, we present an efficient
combinatorial algorithm to find a virtual valuation function with the optimal
(additive) rationality guarantee. Moreover, we show that there exists such a
valuation function that both is individually rational and is minimum (that is,
it is component-wise dominated by any other individually rational, virtual
valuation function that approximately fits the data). Similarly, given upper
bound constraints on the valuation function, we show how to fit the maximum
virtual valuation function with the optimal additive rationality guarantee. In
practice, revealed preference bidding constraints are very demanding. We
explain how approximate rationality can be used to create relaxed revealed
preference constraints in an auction. We then show how combinatorial methods
can be used to implement these relaxed constraints. Worst/best-case welfare
guarantees that result from the use of such mechanisms can be quantified via
the minimum/maximum virtual valuation function
Lottery pricing equilibria
We extend the notion of Combinatorial Walrasian Equilibrium, as defined by Feldman et al. [2013], to settings with budgets. When agents have budgets, the maximum social welfare as traditionally defined is not a suitable benchmark since it is overly optimistic. This motivated the liquid welfare of [Dobzinski and Paes Leme 2014] as an alternative. Observing that no combinatorial Walrasian equilibrium guarantees a non-zero fraction of the maximum liquid welfare in the absence of randomization, we instead work with randomized allocations and extend the notions of liquid welfare and Combinatorial Walrasian Equilibrium accordingly. Our generalization of the Combinatorial Walrasian Equilibrium prices lotteries over bundles of items rather than bundles, and we term it a lottery pricing equilibrium. Our results are two-fold. First, we exhibit an efficient algorithm which turns a randomized allocation with liquid expected welfare W into a lottery pricing equilibrium with liquid expected welfare 3-√5/2 W (≈ 0.3819-W). Next, given access to a demand oracle and an α-approximate oblivious rounding algorithm for the configuration linear program for the welfare maximization problem, we show how to efficiently compute a randomized allocation which is (a) supported on polynomially-many deterministic allocations and (b) obtains [nearly] an α fraction of the optimal liquid expected welfare. In the case of subadditive valuations, combining both results yields an efficient algorithm which computes a lottery pricing equilibrium obtaining a constant fraction of the optimal liquid expected welfare. © Copyright 2016 ACM
Budget Feasible Mechanisms
We study a novel class of mechanism design problems in which the outcomes are
constrained by the payments. This basic class of mechanism design problems
captures many common economic situations, and yet it has not been studied, to
our knowledge, in the past. We focus on the case of procurement auctions in
which sellers have private costs, and the auctioneer aims to maximize a utility
function on subsets of items, under the constraint that the sum of the payments
provided by the mechanism does not exceed a given budget. Standard mechanism
design ideas such as the VCG mechanism and its variants are not applicable
here. We show that, for general functions, the budget constraint can render
mechanisms arbitrarily bad in terms of the utility of the buyer. However, our
main result shows that for the important class of submodular functions, a
bounded approximation ratio is achievable. Better approximation results are
obtained for subclasses of the submodular functions. We explore the space of
budget feasible mechanisms in other domains and give a characterization under
more restricted conditions
Welfare guarantees for proportional allocations
According to the proportional allocation mechanism from the network
optimization literature, users compete for a divisible resource -- such as
bandwidth -- by submitting bids. The mechanism allocates to each user a
fraction of the resource that is proportional to her bid and collects an amount
equal to her bid as payment. Since users act as utility-maximizers, this
naturally defines a proportional allocation game. Recently, Syrgkanis and
Tardos (STOC 2013) quantified the inefficiency of equilibria in this game with
respect to the social welfare and presented a lower bound of 26.8% on the price
of anarchy over coarse-correlated and Bayes-Nash equilibria in the full and
incomplete information settings, respectively. In this paper, we improve this
bound to 50% over both equilibrium concepts. Our analysis is simpler and,
furthermore, we argue that it cannot be improved by arguments that do not take
the equilibrium structure into account. We also extend it to settings with
budget constraints where we show the first constant bound (between 36% and 50%)
on the price of anarchy of the corresponding game with respect to an effective
welfare benchmark that takes budgets into account.Comment: 15 page
POEM: Pricing Longer for Edge Computing in the Device Cloud
Multiple access mobile edge computing has been proposed as a promising
technology to bring computation services close to end users, by making good use
of edge cloud servers. In mobile device clouds (MDC), idle end devices may act
as edge servers to offer computation services for busy end devices. Most
existing auction based incentive mechanisms in MDC focus on only one round
auction without considering the time correlation. Moreover, although existing
single round auctions can also be used for multiple times, users should trade
with higher bids to get more resources in the cascading rounds of auctions,
then their budgets will run out too early to participate in the next auction,
leading to auction failures and the whole benefit may suffer. In this paper, we
formulate the computation offloading problem as a social welfare optimization
problem with given budgets of mobile devices, and consider pricing longer of
mobile devices. This problem is a multiple-choice multi-dimensional 0-1
knapsack problem, which is a NP-hard problem. We propose an auction framework
named MAFL for long-term benefits that runs a single round resource auction in
each round. Extensive simulation results show that the proposed auction
mechanism outperforms the single round by about 55.6% on the revenue on average
and MAFL outperforms existing double auction by about 68.6% in terms of the
revenue.Comment: 8 pages, 1 figure, Accepted by the 18th International Conference on
Algorithms and Architectures for Parallel Processing (ICA3PP
On the Efficiency of the Proportional Allocation Mechanism for Divisible Resources
We study the efficiency of the proportional allocation mechanism, that is
widely used to allocate divisible resources. Each agent submits a bid for each
divisible resource and receives a fraction proportional to her bids. We
quantify the inefficiency of Nash equilibria by studying the Price of Anarchy
(PoA) of the induced game under complete and incomplete information. When
agents' valuations are concave, we show that the Bayesian Nash equilibria can
be arbitrarily inefficient, in contrast to the well-known 4/3 bound for pure
equilibria. Next, we upper bound the PoA over Bayesian equilibria by 2 when
agents' valuations are subadditive, generalizing and strengthening previous
bounds on lattice submodular valuations. Furthermore, we show that this bound
is tight and cannot be improved by any simple or scale-free mechanism. Then we
switch to settings with budget constraints, and we show an improved upper bound
on the PoA over coarse-correlated equilibria. Finally, we prove that the PoA is
exactly 2 for pure equilibria in the polyhedral environment.Comment: To appear in SAGT 201
A Bridge between Liquid and Social Welfare in Combinatorial Auctions with Submodular Bidders
We study incentive compatible mechanisms for Combinatorial Auctions where the
bidders have submodular (or XOS) valuations and are budget-constrained. Our
objective is to maximize the \emph{liquid welfare}, a notion of efficiency for
budget-constrained bidders introduced by Dobzinski and Paes Leme (2014). We
show that some of the known truthful mechanisms that best-approximate the
social welfare for Combinatorial Auctions with submodular bidders through
demand query oracles can be adapted, so that they retain truthfulness and
achieve asymptotically the same approximation guarantees for the liquid
welfare. More specifically, for the problem of optimizing the liquid welfare in
Combinatorial Auctions with submodular bidders, we obtain a universally
truthful randomized -approximate mechanism, where is the number
of items, by adapting the mechanism of Krysta and V\"ocking (2012).
Additionally, motivated by large market assumptions often used in mechanism
design, we introduce a notion of competitive markets and show that in such
markets, liquid welfare can be approximated within a constant factor by a
randomized universally truthful mechanism. Finally, in the Bayesian setting, we
obtain a truthful -approximate mechanism for the case where bidder
valuations are generated as independent samples from a known distribution, by
adapting the results of Feldman, Gravin and Lucier (2014).Comment: AAAI-1
Integrating land financing into subnational fiscal management
Land assets have become an important source of financing capital investments by subnational governments in developing countries. Land assets, often with billions of dollars per transaction, rival and sometimes surpass subnational borrowing or fiscal transfers for capital spending. While reducing the uncertainty surrounding future debt repayment capacity, the use of land-based revenues for financing infrastructure can entail substantial fiscal risks. Land sales often involve less transparency than borrowing. Many sales are conducted off-budget, which makes it easier to divert proceeds into operating budgets. Capital revenues from sales of land assets exert a much more volatile trend and could create an incentive to appropriate auction proceeds for financing the operating budget, particularly in times of budget shortfalls during economic downturns. Furthermore, land collateral and expected future land-value appreciation for bank loans can be linked with macroeconomic risks. It is critical to develop ex ante prudential rules comparable to those governing borrowing, to reduce fiscal risks and the contingent liabilities associated with the land-based revenues for financing infrastructure.Banks&Banking Reform,Public Sector Economics,Debt Markets,Municipal Financial Management,Public&Municipal Finance
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