Faculty of Business

Permanent URI for this communityhttps://hdl.handle.net/10679/4

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Addressing endogeneity in the causal relationship between sustainability and financial performance
(Elsevier, 2019-04) Soytaş, Mehmet Ali; Denizel, M.; Uşar, Damla Durak; Economics; SOYTAŞ, Mehmet Ali; Uşar, Damla Durak
The existing empirical literature on the relationship between corporate sustainability performance and corporate financial performance casts doubt on the direction of this relationship although more studies point out a direction from sustainability to performance. Literature also presents a gap in addressing the mechanism(s) of the relationship that hinders the convergence of the empirical findings and only recently the question of causality is being addressed with modern econometric techniques. We argue that due to the potential endogeneity problem in the relationship, an empirical strategy without a theoretical base may result in inconclusive or misleading conclusions. We address the potential endogeneity problem in the relationship and identify the possible causes of this endogeneity as: (i) firm level heterogeneity in financial returns, (ii) the relationship between firm's productivity level and the marginal cost of sustainability initiatives, and (iii) measurement error. We implement Instrumental Variable (IV) technique to overcome these biases. Our results present empirical evidence to support the hypothesis that corporate sustainability is positively related (possibly causally) with corporate financial performance. We further find that sustainability initiatives are more costly for companies that are more productive; thus, they have less incentive to invest. Finally, measurement error in the sustainability metrics does not play a crucial role.
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Capacitated strategic assortment planning under explicit demand substitution
(Elsevier, 2021-11-01) Çömez-Dolgan, Nagihan; Fescioglu-Unver, N.; Cephe, E.; Şen, A.; Management Information Systems; ÇÖMEZ DOLGAN, Nagihan
Buyers have easier access to a variety of products with the rise of multi-channel distribution strategies and the increase in new product introductions. On the other hand, firms experience greater pressure in offering the correct product variety given that the manufacturing infrastructure often imposes physical and financial constraints in attaining variety. This study examines a firm's optimal assortment planning problem under an exogenous demand model, where each customer has a predetermined preference for each product from a potential set. Proportional demand substitutions are allowed from out-of-assortment products to those available. We show that the problem is NP-complete. We also show that an optimal assortment is composed of some number of the highest margin products, if one product having a higher margin than another implies that the former product has a lower demand rate than the latter. The firm's assortment capacity is fully utilized at the optimum if the customers’ substitution ratio does not exceed a particular threshold. We also introduce several approximate assortment policies that can be easily implemented, and test these policies through extensive numerical analyses. The results reveal that some of the policies can provide less than a 1% profit gap with an optimal solution for a 20-product set. The policy's performance highly depends on the firm's assortment capacity-to-product set size ratio. Moreover, we provide performance bounds for two of these well-performing approximate policies.
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Costly switching from a status quo
(Elsevier, 2018-12) Güney, Begüm; Richter, M.; Economics; GÜNEY, Begüm
We axiomatically characterize a theory of status quo-dependent choice where an agent faces switching costs that depend upon both the status quo and the alternative he switches to. In a choice problem with a status quo, the agent chooses the alternatives that yield the highest utility net of switching cost. This generates status quo bias and also allows for a wide range of reference effects. We examine the behavior of such agents in Prisoner’s Dilemma (PD) games. In a single PD game, switching costs can lead to cooperation. However, across different PD games, it is not “anything goes” and instead we derive necessary and sufficient conditions for cooperation rates to be consistent with our model. We then verify that these conditions are satisfied by Charness et al.’s (2016) experimental data. We also perform a similar analysis for other theories such as models of status quo bias, magical thinking, inequity aversion, and fairness; and find that these theories make either invalidated or looser predictions.
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Expert competition and the internet
(IJEC, 2013) Akçura, Munir Tolga; Ozdemir, Z. D.; Jain, S.; Business Administration; AKÇURA, Münir Tolga
The Internet has become a channel for experts offering their services. We investigate the optimal online channel adoption strategy of a high-quality expert with a brick-and-mortar presence in the face of potential entry by an expert with just an online presence. We find that the high-quality expert does not have the incentive to adopt the online channel unless new entry is imminent. If the incumbent high-quality expert cannot offer a sufficiently high-quality online service, the incumbent expert accommodates entry and provides only a face-to-face service. However, a satisfactory level of online quality allows the incumbent expert to deter entry and to limit what would otherwise be a more intense competition. This paper thus establishes an entry deterrence role for the adoption of the online channel in expert markets. In addition, the results partially explain the reasons behind the quick adoption of the online channel in tax preparation services and physicians’ reluctance to offer online consultations.
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The impact of support on employees’ adaptive behavior: a moderated mediation model
(2021-08-24) Maden-Eyiusta, Ceyda; Yalabik, Z. Y.; Nakiboglu, M. A. B.; Entrepreneurship; EYİUSTA, Ceyda Maden
Purpose – Drawing on the social exchange theory, this study focuses on the impact of perceived organizational support (POS) and perceived supervisor support (PSS) on employees’ adaptive (selling) behavior in a personal selling context. As part of the support-adaptive behavior relationship, the authors also explore the mediating role of psychological empowerment and the moderating role of customer orientation (CO). Design/methodology/approach – Data were collected from 200 salespeople from the financial and pharmaceutical sectors in Turkey. Hypotheses were tested with hierarchical multiple regressions and hierarchical moderated regressions. Findings – Supported salespeople feel more empowered in their jobs and show adaptive (selling) behavior. Our results also show that the impact of support on adaptive selling behavior through empowerment is stronger for salespeople with low CO. Research limitations/implications – This study has two limitations: the generalizability of its findings and cross-sectional design. Still, it significantly contributes to support, empowerment and adaptive behavior literature. Practical implications – By creating a supportive work environment and by training their managers to improve their support skills, organizations boost their employees’ adaptability. Both of these support practices motivate employees to use their discretion in sales situations. Organizations should also evaluate and manage their employees’ level of CO by conducting company surveys and by increasing top management communication. Originality/value – This study tests the mediating role of psychological empowerment on the relationship between POS, PSS and adaptive behavior in the understudied personal selling context. The authors also test the moderating role of CO in the proposed model.
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An integrated analysis of capacity allocation and patient scheduling in presence of seasonal walk-ins
(Springer Nature, 2019-06) Çayırlı, Tuğba; Dursun, P.; Güneş, E. D.; Business Administration; ÇAYIRLI, Tuğba
This study analyzes two decision levels in appointment system design in the context of clinics that face seasonal demand for scheduled and walk-in patients. The macro-level problem addresses access rules dealing with capacity allocation decisions in terms of how many slots to reserve for walk-ins and scheduled patients given fixed daily capacity for the clinic session. The micro-level problem addresses scheduling rules determining the specific time slots for scheduled arrivals. A fully-integrated simulation model is developed where daily demand actualized at the macro level becomes an input to the micro model that simulates the in-clinic dynamics, such as the arrivals of walk-ins and scheduled patients, as well as stochastic service times. The proposed integrated approach is shown to improve decision-making by considering patient lead times (i.e., indirect wait), direct wait times, and clinic overtime as relevant measures of performance. The traditional methods for evaluating appointment system performance are extended to incorporate multiple trade-offs. This allows combining both direct wait and indirect wait that are generally addressed separately due to time scale differences (minutes vs. days). The results confirm the benefits of addressing both decision levels in appointment system design simultaneously. We investigate how environmental factors affect the performance and the choice of appointment systems. The most critical environmental factors emerge as the demand load, seasonality level, and percentage of walk-ins, listed in the decreasing order of importance.
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Multi-plant manufacturing assortment planning in the presence of transshipments
(Elsevier, 2023-11-01) Çömez-Dolgan, Nagihan; Dağ, H.; Fescioglu-Unver, N.; Şen, A.; Management Information Systems; ÇÖMEZ DOLGAN, Nagihan
In this study, we consider the assortment planning problem of a manufacturing firm with multiple plants. Making a plant capable of producing a product is costly, therefore the firm cannot manufacture every product in every plant. In case a customer's order in a particular region is not available in the closest plant, another plant can ship the product using transshipment, but at an extra transportation cost. If a demanded product is not produced in any plant, substitution from first choice to a second choice is also considered, which can be either satisfied by the closest plant, or by transshipment. The problem is to jointly determine assortments in all plants such that total profit after assortment and transshipment costs is maximized. The resulting problem is complex as transshipments and substitutions are intertwined to affect assortment decisions. We show that the optimal assortments are nested, i.e., the assortment of a plant with a smaller market share is a subset of the assortment of a plant with a larger share. The common assortment of all locations is shown to be in the popular set (i.e., no leapfrogging in product popularities), and a sufficient condition on substitution rate is derived for each individual assortment to be in the popular set. We conduct an extensive numerical study to understand the effects of allowing transshipments on resulting assortments. Moreover, we introduce approximate assortment planning algorithms that benefit from the derived structural properties, which are shown to generate near-optimal assortments in a broad range of instances tested.
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Noninfluentials and information dissemination in the microblogging community
(Springer Nature, 2017) Akçura, Munir Tolga; Altinkemer, K.; Chen, H.; Business Administration; AKÇURA, Münir Tolga
Firms are increasingly focusing on understanding and managing their social media strategies in order to create discussions and optimize the spread of news in their communities. Most prior studies on information dissemination have mainly focused on the roles of influentials but ignored the essential for noninfluentials. To fill this gap, this paper takes a holistic view of the information dissemination process and investigates how the participation of both influentials and noninfluentials plays a role in affecting the volume and sentiment of microblogs, which are precursors to raise awareness and attraction for brands. To test our hypotheses, we build a novel econometric model and apply it to a dataset collected from the popular microblogging site Twitter. We have the following main results: (1) back-and-forth-type discussions and retweets are effective in generating awareness and positive attractiveness; (2) influentials or mavens (who have many followers but seldom follow others) help generate initial sparks toward microblogging, but during the cascading periods, the noninfluentials play an important role in driving the conversations; and (3) new users who gradually join the discussions also help increase awareness, although they may not generate a positive sentiment. Our results provide important implications for mediating consumer interactions and firms’ marketing strategies.
Open Access
On efficient computation of equilibrium under social coalition structures
(TÜBİTAK, 2020) Caskurlu, B.; Ekici, Özgür; Kizilkaya, F. E.; Economics; EKİCİ, Özgün
In game-theoretic settings the key notion of analysis is an equilibrium, which is a profile of agent strategies such that no viable coalition of agents can improve upon their coalitional welfare by jointly changing their strategies. A Nash equilibrium, where viable coalitions are only singletons, and a super strong equilibrium, where every coalition is deemed viable, are two extreme scenarios in regard to coalition formation. A recent trend in the literature is to consider equilibrium notions that allow for coalition formation in between these two extremes and which are suitable to model social coalition structures that arise in various real-life settings. The recent literature considered the question on the existence of equilibria under social coalition structures mainly in Resource Selection Games (RSGs), due to the simplicity of this game form and its wide range of application domains. We take the question on the existence of equilibria under social coalition structures from the perspective of computational complexity theory. We study the problem of deciding the existence of an equilibrium in RSGs with respect to a given social coalition structure. For an arbitrary coalition structure, we show that it is computationally intractable to decide whether an equilibrium exists even in very restricted settings of RSGs. In certain settings where an equilibrium is guaranteed to exist we give polynomial-time algorithms to find an equilibrium.
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On existence of equilibrium under social coalition structures
(Cambridge University Press, 2022-02) Caskurlu, B.; Ekici, Özgün; Kizilkaya, F. E.; Economics; EKİCİ, Özgün
In a strategic-form game, a strategy profile is an equilibrium if no viable coalition of agents (or players) benefits (in the Pareto sense) from jointly changing their strategies. Weaker or stronger equilibrium notions can be defined by considering various restrictions on coalition formation. For instance, in a Nash equilibrium, it is assumed that viable coalitions are singletons, and in a super strong equilibrium, it is assumed that every coalition is viable. Restrictions on coalition formation can be justified by communication limitations, coordination problems, or institutional constraints. In this paper, inspired by social structures in various real-life scenarios, we introduce certain restrictions on coalition formation, and on their basis, we introduce a number of equilibrium notions. As an application, we study our equilibrium notions in resource selection games (RSGs), and we present a complete set of existence and nonexistence results for general RSGs and their important special cases.
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Online intermediary as a channel for selling quality-differentiated services
(Wiley, 2015-02) Akçura, Munir Tolga; Ozdemir, Z. D.; Rahman, M. S.; Business Administration; AKÇURA, Münir Tolga
When deciding whether to utilize an online intermediary in addition to their own distribution channels, quality differentiated service providers face the trade-off between the benefit of extended reach and the threat of increased competition. Using an analytical framework, we analyze when and how service providers may utilize an online intermediary to their advantage in the presence of advance selling (i.e., selling a service at an early date for future consumption). In general, when an online intermediary is used, the competition effect dominates the reach effect and leads to a falling price trend. Interestingly, we find that the negative effect of increased competition on profits, due to intermediary usage, can be reversed by committing to self-imposed participation limits (i.e., selling only a predetermined amount of services through the online intermediary). This ensures that the service provider is better off selling through both its own site and the online intermediary, rather than selling exclusively using either channel.
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Outpatient appointment scheduling in presence of seasonal walk-ins
(Springer Nature, 2014-04) Çayırlı, Tuğba; Güneş, E. D.; Business Administration; ÇAYIRLI, Tuğba
This study investigates appointment systems (AS), as combinations of access rules and appointment-scheduling rules, explicitly designed for dealing with walk-in seasonality. In terms of 'access rules', strategies are tested for adjusting capacity through intra-week, or monthly seasonality of walk-ins, or their combined effects. In terms of 'appointment rules', strategies are tested to determine which particular slots to double-book or leave open in cases where seasonal walk-in rates exceed or fall short of the overall yearly rate. In that regard, this study integrates capacity and appointment decisions, which are usually addressed in an isolated manner in previous studies. Simulation optimization is used to derive heuristic solutions to the appointment-scheduling problem, and the findings are compared in terms of in-clinic measures of patient wait time, physician idle time and overtime. The goal is to provide practical guidelines for healthcare practitioners on how to best design their AS when seasonal walk-ins exist.
Open Access
Price of regulations: Regulatory costs and the cross-section of stock returns
(Oxford University Press, 2024-01) Ince, B.; Özsöylev, Han Nazmi; International Finance; ÖZSÖYLEV, Han Nazmi
Regulations introduce significant fixed costs and add to operating leverage. Fixed regulatory costs that contribute to operating leverage should generate a risk premium. To explore whether such a premium exists, we introduce a measure of "regulatory operating leverage" that reflects the importance of fixed regulatory costs in a firm's cost structure. Regulatory operating leverage predicts stock returns in the cross-section, and a zero-cost high-low regulatory operating leverage strategy generates positive and significant risk-adjusted return. Finally, the impact of regulatory operating leverage on returns is due to the (systematic) risk contribution of fixed regulatory costs.
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Recovery decisions of a producer in a legislative disposal fee environment
(Elsevier, 2012-01-16) Özdemir, Ö.; Denizel, Meltem; Guide Jr., V. D. R.; Industrial Engineering; DENİZEL, Meltem
The main objectives of the environmental legislation originating from extended producer responsibility (EPR) principle are to lead producers to undertake recovery initiatives for their end-of-use products and to promote environmentally desirable product design. It is still controversial whether current implementations of EPR principle are effective in attaining these objectives. This study seeks to answer the following questions: (1) What is the impact of EPR legislation on the product recovery decisions of producers? (2) How do the redesign opportunities (i.e., design for disassembly) affect the willingness of producers for product recovery? (3) How do the investment needs to start recovery practices and the reluctance of producers to allocate sufficient funds for this purpose affect the optimal recovery decisions? We use stylized economic models to represent the implementation in practice and solving our models we obtain closed form and numerical solutions that help us to see the impact of various parameters on the optimal decisions of a producer. Our findings indicate that redesign opportunities encourage producers for more recovery, however the reluctance of producers to cover the initial investments may substantially reduce the effectiveness of the legislation and the recovery amounts.
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What determines REIT returns in Turkey? An application of time-varying arbitrage pricing model in an emerging REIT market
(Bilgesel Yayıncılık, 2013) Erol, Işıl; İleri, A.; International Finance; EROL, Işıl
This paper investigates the macroeconomic sources of time-varying risk premia in Turkish REIT industry within the arbitrage pricing theory framework. Turkish REIT industry differs substantially from the global REIT market as Turkish REITs do not have to pay out dividends, yet enjoy the exemption from paying corporate taxes, and have highly concentrated ownership structure. These fundamental differences have significant impacts on the performance of REITs compared to other stocks listed on Borsa Istanbul (BIST), especially in terms of the inflationhedging characteristics and time-varying systematic risk behaviour. This article evaluates the Turkish REIT industry by using a time-varying multifactor model, which compares the REIT industry excess returns with various macroeconomic factors, including GDP growth, industrial production growth, inflation risk premium, and stock market risk premium. Our results provide the evidence of time-varying linkages among macroeconomic risks and the conditional first and second moments of excess returns on REITs. We find that among the macroeconomic factors, inflation risk appears to be the major concern in REIT investment. Additionally, Turkish REITs behave more like stocks than real estate. The documented perverse inflation hedges of REITs, the positive correlation between REIT returns and volatility of real economic activity, and the significant influence of ISE equity risk premium on REIT returns can be quoted as the indications of deviation of REITs’ performance from real estate performance. If REITs behave more like stocks than real estate, the diversification benefits of having REITs in a multi-asset portfolio is seriously reduced.

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