On the Complexity of Dynamic Mechanism Design

We introduce a dynamic mechanism design problem in which the designer wants to offer for sale an item to an agent, and another item to the same agent at some point in the future. The agent's joint distribution of valuations for the two items is known, and the agent knows the valuation for the current item (but not for the one in the future). The designer seeks to maximize expected revenue, and the auction must be deterministic, truthful, and ex post individually rational. The optimum mechanism involves a protocol whereby the seller elicits the buyer's current valuation, and based on the bid makes two take-it-or-leave-it offers, one for now and one for the future. We show that finding the optimum deterministic mechanism in this situation - arguably the simplest meaningful dynamic mechanism design problem imaginable - is NP-hard. We also prove several positive results, among them a polynomial linear programming-based algorithm for the optimum randomized auction (even for many bidders and periods), and we show strong separations in revenue between non-adaptive, adaptive, and randomized auctions, even when the valuations in the two periods are uncorrelated. Finally, for the same problem in an environment in which contracts cannot be enforced, and thus perfection of equilibrium is necessary, we show that the optimum randomized mechanism requires multiple rounds of cheap talk-like interactions

On Learning Algorithms for Nash Equilibria

Third International Symposium, SAGT 2010, Athens, Greece, October 18-20, 2010. ProceedingsCan learning algorithms find a Nash equilibrium? This is a natural question for several reasons. Learning algorithms resemble the behavior of players in many naturally arising games, and thus results on the convergence or non-convergence properties of such dynamics may inform our understanding of the applicability of Nash equilibria as a plausible solution concept in some settings. A second reason for asking this question is in the hope of being able to prove an impossibility result, not dependent on complexity assumptions, for computing Nash equilibria via a restricted class of reasonable algorithms. In this work, we begin to answer this question by considering the dynamics of the standard multiplicative weights update learning algorithms (which are known to converge to a Nash equilibrium for zero-sum games). We revisit a 3×3 game defined by Shapley [10] in the 1950s in order to establish that fictitious play does not converge in general games. For this simple game, we show via a potential function argument that in a variety of settings the multiplicative updates algorithm impressively fails to find the unique Nash equilibrium, in that the cumulative distributions of players produced by learning dynamics actually drift away from the equilibrium

Assessing service quality and customer behavioral responses in hospital outpatient services: a formative measurement approach

Purpose – In contrast to the reflective approach of service quality measurement, this paper proposes and validates a parsimonious multidimensional second-order formatively measured model of service quality for primary healthcare services provided by hospital outpatient departments. The index’s empirical validity is examined by investigating the strength of its relationship with certain behavioral responses such as patient satisfaction and behavioral intentions.  Design/methodology/approach - Data were collected through a stratified random sampling from eight hospital outpatient departments in Greece. Covariance-based structural equation modelling techniques were used to validate the proposed service quality index and further investigate its effect on patient satisfaction and behavioral intention.  Findings - The data analysis indicated that the proposed formative index is fully functional with medical care being the factor mostly contributes to service quality perception, followed by administrative service and staff performance, facilities condition and nursing care. It, further, confirmed the partial mediating role of satisfaction as it enhances the high impact of service quality on behavioral intentions. Research limitations – The relationships among hospital outpatient departments service quality, patient satisfaction and behavioral intentions were validated with data from one country and a healthcare system which is state driven and funded.  Practical implications - An understanding of hospital primary healthcare service quality formation is important to healthcare decision makers because it offers them the opportunity to consider patients’ needs and wants and take the appropriate actions for improving the relevant underling procedures in a more efficient manner in order to achieve favorable behavioral responses.  Originality/value - The paper manages to propose and empirically evaluate a formatively measured approach of service quality and investigate the effects of the proposed index on patient satisfaction and behavioral intention, especially in the hospital outpatient services context in Greece

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

The Complexity of Optimal Auction Design

This dissertation provides a complexity-theoretic critique of Myerson's theorem, one of Mechanism Design's crown jewels, for which Myerson was awarded the 2007 Nobel Memorial Prize in Economic Sciences. This theorem gives a remarkably crisp solution to the problem faced by a monopolist wishing to sell a single item to a number of interested, rational bidders, whose valuations for the item are distributed independently according to some given distributions; the monopolist's goal is to design an auction that will maximize her expected revenue, while at the same time incentivizing the bidders to bid their true value for the item. Myerson solves this problem of designing the revenue-maximizing auction, through an elegant transformation of the valuation space, and a reduction to the problem of designing the social welfare-maximizing auction (i.e. allocating the item to the bidder who values it the most). This latter problem is well understood, and it admits a deterministic (i.e. the auctioneer does not have to flip any coins) and simple solution: the Vickrey (or second-price) auction. In the present dissertation we explore the trade-offs between the plausibility of this result and its tractability:First, we consider what happens as we shift away from the simple setting of Myerson to more complex settings, and, in particular, to the case of bidders with arbitrarily correlated valuations. Is a characterization as crisp and elegant as Myerson's still possible? In Chapter 2 we provide a negative answer: we show that, for three or more bidders, the problem of computing a deterministic, ex-post incentive compatible and individually rational auction that maximizes revenue is NP-complete --in fact, inapproximable. Even for the case of two bidders, where, as we show, the revenue-maximizing auction is easy to compute, it admits nonetheless no obvious natural interpretation a-la Myerson.Then, motivated by the subtle interplay between social welfare- and revenue-maximizing auctions implied by Myerson's theorem, we study the trade-off between those two objectives for various types of auctions. We show that, as one moves from the least plausible auction format to the most plausible one, the problem of reconciling revenue and welfare becomes less and less tractable. Indeed, if one is willing to settle for randomized solutions, then auctions that fare well with respect to both objectives simultaneously are possible, as shown by Myerson and Satterthwaite. For deterministic auctions on the other hand, we show in Chapter 3 that it is NP-hard to exactly compute the optimal trade-off (Pareto) curve between those two objectives. On the positive side, we show how this curve can be approximated within arbitrary precision for some settings of interest. Finally, when one is only allowed to use variants of the simple Vickrey auction, we show in Chapter 4 that there exist auctions that achieve constant factor approximations of the optimal revenue and social welfare simultaneously

Organization network of primary health care and local community

OBJECTIVE: The objective of this research is to define the factors that affect the selection of Primary Health Care Services. MATERIAL AND METHOD: For the purposes of the research, a total of 300 users of Primary Health services were interviewed with the common the fact that they were living in a rural or semi-urban area, in 4 different hospitals of Athens. The research was conducted with the method of personal interviews with the use of a well-designed questionnaire and there were selected 244 questionnaires. The sampling method that was used was the Stratified random sampling and the data analysis was based on simple statistics and test statistics and linear regression. RESULTS: The results of the research show that the users evaluate with a low score the quality of health services provided by the health center in their living place (giving a score of 5,34 out of 10) and evaluate with a bigger score the quality of health services provided by the Hospitals in Athens (8,23 out of 10 ). According to the linear regression results (see table 3) the evaluation of the health center in the responders living area is also related positively with the distance in kilometers from the living area and it is negatively related with Education level and Cost of transportation. CONCLUSION: There is a strong evidence that the there is a problem in the function of the Primary Health Care System in rural and semi-rural areas, thus the sector of Secondary and Tertiary Health Service is overloaded with the additional cost of Primary Health Service support. It will be interesting evaluate the contribution of local Authorities in the creation of an effective Primary Health Service network which is compatible with a holistic approach of the notion of health.ΣΚΟΠΟΣ: Σκοπός της παρούσας μελέτης είναι αποτύπωση των παραγόντων για την επιλογή υπηρεσιών Πρωτοβάθμιας Φροντίδας Υγείας.ΥΛΙΚΟ ΚΑΙ ΜΕΘΟΔΟΣ: Το υλικό αποτέλεσαν 300 χρήστες υπηρεσιών των εξωτερικών ιατρείων 4 μεγάλων Νοσοκομείων της Αθήνας με μόνιμο τόπο κατοικίας εκτός Αθήνας. Η μεθοδολογία που ακολουθήθηκε ήταν οι προσωπικές συνεντεύξεις με τη βοήθεια ερωτηματολογίου με ερωτήσει κλειστού τύπου και συλλέχθηκαν 244 ερωτηματολόγια. Ως δειγματοληπτική μέθοδος χρησιμοποιήθηκε η στρωματοποιημένη τυχαία δειγματοληψία και η ανάλυση των δεδομένων έγινε με τη χρήση της περιγραφικής στατιστικής, την εφαρμογή στατιστικού ελέγχου υποθέσεων και γραμμική παλινδρόμηση.ΑΠΟΤΕΛΕΣΜΑΤΑ: Οι ερωτώμενοι βαθμολογούν με μικρό βαθμό το κέντρο υγείας στον τόπο μόνιμης κατοικίας τους (5,34 στη δεκάβαθμη κλίμακα) και με υψηλό τα εξωτερικά Ιατρεία των Νοσοκομείων της Αθήνας (8,23 στη δεκάβαθμη κλίμακα). Ως προς το μέγεθος της εξάρτησης του βαθμού αξιολόγησης στη γραμμική παλινδρόμηση (βλ. πίνακα 3), η θετικά ισχυρότερη αφορά την Απόσταση από τον τόπο κατοικίας. Αντίστοιχα οι αρνητικές ισχυρότερες κατά σειρά εξάρτησης είναι το Επίπεδο εκπαίδευσης και το Κόστος μεταφοράς στην Αθήνα. ΣΥΜΠΕΡΑΣΜΑΤΑ: Υπάρχει ισχυρή ένδειξη για προβληματική λειτουργία του συστήματος ΠΦΥ στις αγροτικές και ημιαστικές περιοχές, με αποτέλεσμα την επιβάρυνση του τομέα της Δευτεροβάθμιας και Τριτοβάθμιας περίθαλψης. Θα ήταν ενδιαφέρον να εξεταστεί η ενεργός συμμετοχής της Τοπικής Αυτοδιοίκησης στην δημιουργία αποτελεσματικού δικτύου Πρωτοβάθμιας Φροντίδας Υγείας συμβατό με την ολιστική αντιμετώπιση της έννοιας της υγείας