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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6
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Publication Open Access Random assignment under weak preferences(Elsevier, 2009) Department of Economics; Yılmaz, Özgür; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; 108638The natural preference domain for many practical settings of the assignment problems is the one in which agents are allowed to be indifferent between objects, the weak preference domain. Most of the existing work on assignment problems assumes strict preferences. There are important exceptions. but they provide solutions only to the assignment problems with a social endowment, where agents own objects collectively and there are no private endowments. We consider the general class of assignment problems with private endowments and a social endowment. Our main contribution is a recursive solution for the weak preference domain. Our solution satisfies individual rationality, ordinal efficiency and a recently introduced fairness axiom, no justified-envy.Publication Open Access The probabilistic serial mechanism with private endowments(Elsevier, 2010) Department of Economics; Yılmaz, Özgür; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; 108638A random assignment is ordinally efficient if it is not stochastically dominated with respect to individual preferences over sure objects. When there are no private endowments, the set of ordinally efficient random assignments is characterized by the eating algorithm (Bogomolnaia and Moulin, 2001). When there are private endowments, the main requirement is individual rationality; however, the eating algorithm fails to deliver this property. Our contribution is the natural generalization of the eating algorithm for this general class of problems. The family of this generalized eating algorithm characterizes the set of individually rational and ordinally efficient random assignments. A special solution in this family, the individually rational probabilistic serial (PS(IR)), also achieves a new fairness axiom, no justified-envy. However, it is not immune to strategic manipulation. We show that individual rationality, no justified-envy and strategy-proofness are incompatible.Publication Open Access Majority choice of an income-targeted educational voucher(American Economic Association (AEA), 2018) Epple, Dennis; Romano, Richard; Department of Economics; Sarpça, Sinan; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; 52406A model of majority choice of voucher characteristics with quantitative counterpart explains observed income eligibility requirements for educational vouchers. Households differ by income and preference for religious schooling. They elect a policy maker who chooses public school expenditure, a voucher, a maximum income for voucher eligibility, and a tax to finance public expenditure. Equilibrium has a voucher below per student public expenditure, an eligibility threshold near 300 percent of the poverty level, and a majority in public school though with substantial voucher usage, all properties typical of US voucher programs. Disallowing a voucher leads to higher per student public expenditure.Publication Open Access Production control of a pull system with production and demand uncertainty(Institute of Electrical and Electronics Engineers (IEEE), 2002) Department of Business Administration; Tan, Barış; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 28600We consider a continuous material-flow manufacturing system with an unreliable production system and a variable demand source which switches randomly between zero and a maximum level. The failure and repair times of the production system and the switching times of the demand source are assumed to be exponentially distributed random variables. The optimal production flow control policy that minimizes the expected average inventory carrying and backlog costs is characterized as a double-hedging policy. The optimal hedging levels are determined analytically by minimizing the closed-form expression of the cost function. We investigate two approximate single hedging policies. It is empirically shown that an approximate policy that uses a single hedging level which is the sum of a production uncertainty term and a demand uncertainty term gives accurate results for the expected average cost.Publication Open Access Capacity planning for effective cohorting of hemodialysis patients during the coronavirus pandemic: a case study(Elsevier, 2023) Bozkır, C.D.C.; Özmemiş, C.; Kurbanzade, A.K.; Balçık, B.; Tuğlular, S.; Department of Business Administration; Güneş, Evrim Didem; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 51391Planning treatments of different types of patients have become challenging in hemodialysis clinics during the COVID-19 pandemic due to increased demands and uncertainties. In this study, we address capacity planning decisions of a hemodialysis clinic, located within a major public hospital in Istanbul, which serves both infected and uninfected patients during the COVID-19 pandemic with limited resources (i.e., dialysis machines). The clinic currently applies a 3-unit cohorting strategy to treat different types of patients (i.e., uninfected, infected, suspected) in separate units and at different times to mitigate the risk of infection spread risk. Accordingly, at the beginning of each week, the clinic needs to allocate the available dialysis machines to each unit that serves different patient cohorts. However, given the uncertainties in the number of different types of patients that will need dialysis each day, it is a challenge to determine which capacity configuration would minimize the overlapping treatment sessions of different cohorts over a week. We represent the uncertainties in the number of patients by a set of scenarios and present a stochastic programming approach to support capacity allocation decisions of the clinic. We present a case study based on the real-world patient data obtained from the hemodialysis clinic to illustrate the effectiveness of the proposed model. We also compare the performance of different cohorting strategies with three and two patient cohorts.Publication Open Access Modeling and analysis of an auction-based logistics market(Elsevier, 2008) Ağralı, Semra; Department of Business Administration; Department of Industrial Engineering; Tan, Barış; Karaesmen, Fikri; Faculty Member; Faculty Member; Department of Business Administration; Department of Industrial Engineering; College of Administrative Sciences and Economics; College of Engineering; 28600; 3579We consider a logistics spot market where the transportation orders from a number of firms are matched with two types of carriers through a reverse auction. In the spot market, local carriers compete with in-transit carriers that have lower costs. In order to analyze the effects of implementing a logistics spot market on these three parties: firms, local carriers, and in-transit carriers and also the effects of various system parameters, we develop a two-stage stochastic model. We first model the auction in a static setting and determine the expected auction price based on the number of carriers engaging in the auction and their cost distributions. We then develop a continuous-time Markov chain model to evaluate the performance of the system in a dynamic setting with random arrivals and possible abandonment of orders and carriers. By combining these two models, we evaluate the performance measures such as the expected auction price, price paid to the carriers, distribution of orders between local and in-transit carriers, and expected number of carriers and orders waiting at the logistics center in the long run. We present analytical and computational results related to the performance of the system and discuss operation of such a logistics spot market in Turkey.Publication Open Access Choice, consideration sets, and attribute filters(American Economic Association (AEA), 2018) Department of Economics; Kimya, Mert; Faculty Member; Department of Economics; College of Administrative Sciences and EconomicsIt is well known that decision makers do not always consider all of the available alternatives when making a choice. When the alternatives have attributes, these attributes provide a natural way to form the consideration set. I assume a procedure in which the decision maker uses the relative ranking of the alternatives on each attribute to reduce the size of the choice set. I provide a characterization of the procedure and illustrate how to identify the underlying preference and consideration set. The model explains certain choice anomalies such as the attraction and the compromise effects.Publication Open Access Positioning multicountry brands: the impact of variation in cultural values and competitive set(American Marketing Association (AMA), 2017) Batra, Rajeev; Zhang, Y. Charles; Feinberg, Fred M.; Department of Business Administration; Aydınoğlu, Nilüfer Zümrüt; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 114037Building on cultural values research, the authors identify specific image attributes on which multicountry brands should position themselves consistently across markets. Leveraging prior research, they identify three life values that are most equal (benevolence, universalism, and self-direction) and two that are least equal (power and hedonism) in cross-national importance. The authors link specific brand image attributes (e.g., friendly, social, elite style, arrogant) to these life values through empirical data and semantic analysis. Using an extensive field data set on consumer perceptions and preferences from 22 countries regarding more than 1,700 brands, the authors then show that greater global consistency of a brand's image decreases overall brand attitudes if the specific image attribute is one that is not equally desired worldwide. They also find that the attitudinal impact of a multicountry brand's positioning consistency on commonly valued image attributes is greater when the set of competitors the brand faces across its markets is more homogeneous. The authors discuss implications for global brand management theory and practice.Publication Open Access Front-office multitasking between service encounters and back-office tasks(Elsevier, 2020) Legros, Benjamin; Jouini, Oualid; Koole, Ger; Department of Business Administration; Karaesmen, Zeynep Akşin; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 4534We model the work of a front-line service worker as a queueing system. The server interacts with customers in a multi-stage process with random durations. Some stages require an interaction between server and customer, while other stages are performed by the customer as a self-service task or with the help of another resource. Random arrivals by customers at the beginning and during an encounter create random lengths of idle time in the work of the server (breaks and interludes respectively). The server considers treatment of an infinite amount of back-office tasks, or tasks that do not require interaction with the customer, during these idle times. We consider an optimal control problem for the server's work. The main question we explore is whether to use the interludes in service encounters for treating back-office, when the latter incur switching times. Under certain operating environments, working on back-office during interludes is shown to be valuable. Switching times play a critical role in the optimal control of the server's work, at times leading the server to prefer remaining idle during breaks and interludes, instead of working on back-office, and at others to continue back-office in the presence of waiting customers. The optimal policy for use of the interludes is one with multiple thresholds depending on both the customers queueing for service, and the ones who are in-service. We illustrate that in settings with multiple interludes in an encounter, if at all, the back-office work should be concentrated on fewer, longer and later interludes.Publication Open Access Building social cohesion in ethnically mixed schools: an intervention on perspective taking(Oxford University Press (OUP), 2021) Alan, Şule; Baysan, Ceren; Kubilay, Elif; Department of Economics; Gümren, Mert; Researcher; Department of Economics; Graduate School of Social Sciences and HumanitiesWe evaluate the effect of an educational program that aims to build social cohesion in ethnically mixed schools by developing perspective-taking ability in children. The program is implemented in Turkish elementary schools affected by a large influx of Syrian refugee children. We measure a comprehensive set of outcomes that characterize a cohesive school environment, including peer violence incidents, the prevalence of interethnic social ties, and prosocial behavior. Using randomized variation in program implementation, we find that the program significantly lowers peer violence and victimization on school grounds. The program also reduces the likelihood of social exclusion and increases interethnic social ties in the classroom. We find that the program significantly improves prosocial behavior, measured by incentivized tasks: treated students exhibit significantly higher trust, reciprocity, and altruism toward each other as well as toward anonymous out-school peers. We show that this enhanced prosociality is welfare improving from the ex post payoff perspective. We investigate multiple channels that could explain the results, including ethnic bias, impulsivity, empathetic concern, emotional intelligence, behavioral norms, and perspective taking. Children's increased effort to take others' perspectives emerges as the most robust mechanism to explain our results.