The risk-averse newsvendor problem with random capacity

We study the effect of capacity uncertainty on the inventory decisions of a risk-averse newsvendor. We consider two well-known risk criteria, namely Value-at-Risk (VaR) included as a constraint and Conditional Value-at-Risk (CVaR). For the risk-neutral newsvendor, we find that the optimal order quantity is not affected by the capacity uncertainty. However, this result does not hold for the risk-averse newsvendor problem. Specifically, we find that capacity uncertainty decreases the order quantity under the CVaR criterion. Under the VaR constraint, capacity uncertainty leads to an order decrease for low confidence levels, but to an order increase for high confidence levels. This implies that the risk criterion should be carefully selected as it has an important effect on inventory decisions. This is shown for the newsvendor problem, but is also likely to hold for other inventory control problems that future research can address.     

Risk-averse decision making in overbooking problem

Traditional literature studying overbooking problems focuses on risk-neutral decision makers. In this paper, we propose a multi-period overbooking model incorporating risk-aversion and extend well-known structural results (the 3-region policy) under the risk-neutral case to the risk-averse one on the basis of an exponential utility function. We also show that the optimal policy for the risk-neutral decision maker can be obtained by letting the risk-aversion parameter approach to zero under the risk-averse case. Therefore, the extant results under the risk-neutral case can be interpreted as a special case of ours. We also investigate how the optimal policy changes with some cost parameters and the decision maker's degree of risk-aversion. Numerical results suggest that the optimal bounds in the 3-region policy may increase or decrease with the decision maker's degree of risk-aversion.     

基于CVaR风险测度标准的价格补贴策略下的协调研究

基于条件风险值模型(CVaR),探讨了在一个风险中性制造商和一个风险规避零售商组成的制造商领导的斯塔克伯格博弈供应链中,制造商如何与风险规避零售商订立批发价契约以最大化其期望利润的问题。设计了价格补贴的契约协调机制,给出了该机制下风险规避程度对零售商和制造商最优决策的影响。证明了在一定的实施条件下,制造商通过设立价格补贴机制,可改善供应链双方利润与供应链效率。最后,用算例验证了模型和理论分析的可行性。     

CVaR准则下两条供应链的促销努力竞争与链内协调研究

研究两条供应链相互竞争下决策者风险厌恶程度的影响和链内协调问题。针对两条分别由风险中性制造商和风险厌恶零售商组成、进行订货与促销竞争的可替代产品供应链,假定需求随机且依赖于促销努力水平与产品合格率,利用条件风险值(CVaR)方法和博弈理论建立了对应两条供应链均为分散式供应链(DD模式)、均为集中式供应链(II模式)、一条为分散式供应链一条为集中式供应链(DI模式)的EPEC、Nash和MPEC竞争决策模型,给出了三种模式下的竞争均衡决策、以及零售商为风险厌恶者时可实现链内协调的回购加促销补贴契约。进一步分析了零售商风险中性情况。最后的算例验证了模型的合理性和协调契约的有效性。研究表明,零售商越厌恶风险,其订货量越低;产品合格率越高,零售商的促销努力水平越大;供应链协调是供应链竞争下的占优策略。     

Newsvendor solutions via conditional value-at-risk minimization

In this paper, we consider the minimization of the conditional value-at-risk (CVaR), a most preferable risk measure in financial risk management, in the context of the well-known single-period newsvendor problem, which is originally formulated as the maximization of the expected profit or the minimization of the expected cost. We show that downside risk measures including the CVaR are tractable in the problem due to their convexity, and consequently, under mild assumptions on the probability distribution of products’ demand, we provide analytical solutions or linear programming (LP) formulation of the minimization of the CVaR measures defined with two different loss functions. Numerical examples are also exhibited, clarifying the difference among the models analyzed in this paper, and demonstrating the efficiency of the LP solutions.     

Assessing mutual funds’ corporate social responsibility: a multistakeholder-AHP based methodology

Currently, stochastic optimization on the one hand and multi-objective optimization on the other hand are rich and well-established special fields of Operations Research. Much less developed, however, is their intersection: the analysis of decision problems involving multiple objectives and stochastically represented uncertainty simultaneously. This is amazing, since in economic and managerial applications, the features of multiple decision criteria and uncertainty are very frequently co-occurring. Part of the existing quantitative approaches to deal with problems of this class apply scalarization techniques in order to reduce a given stochastic multi-objective problem to a stochastic single-objective one. The present article gives an overview over a second strand of the recent literature, namely methods that preserve the multi-objective nature of the problem during the computational analysis. We survey publications assuming a risk-neutral decision maker, but also articles addressing the situation where the decision maker is risk-averse. In the second case, modern risk measures play a prominent role, and generalizations of stochastic orders from the univariate to the multivariate case have recently turned out as a promising methodological tool. Modeling questions as well as issues of computational solution are discussed.     

An exact method for constrained maximization of the conditional value-at-risk of a class of stochastic submodular functions

We consider a class of risk-averse submodular maximization problems (RASM) where the objective is the conditional value-at-risk (CVaR) of a random nondecreasing submodular function at a given risk level. We propose valid inequalities and an exact general method for solving RASM under the assumption that we have an efficient oracle that computes the CVaR of the random function. We demonstrate the proposed method on a stochastic set covering problem that admits an efficient CVaR oracle for the random coverage function.     

A multi-product risk-averse newsvendor with exponential utility function

We consider a multi-product newsvendor using an exponential utility function. We first establish a few basic properties for the newsvendor regarding the convexity of the model and monotonicity of the impact of risk aversion on the solution.When the product demands are independent and the ratio of the degree of risk aversion to the number of products is sufficiently small, we obtain closed-form approximations of the optimal order quantities. The approximations are as easy to compute as the risk-neutral solution. We prove that when this ratio approaches zero, the risk-averse solution converges to the corresponding risk-neutral solution. When the product demands are positively (negatively) correlated, we show that risk aversion leads to lower (higher) optimal order quantities than the solution with independent demands.Using a numerical study, we examine convergence rates of the approximations and thoroughly study the interplay of demand correlation and risk aversion. The numerical study confirms our analytical results and further shows that an increased risk aversion does not always lead to lower order quantities, when demands are strongly negatively correlated.     

基于条件风险值准则的供应链回购契约协调策略

研究了由具有风险偏好的零售商和风险中性的供应商组成的两级供应链回购契约协调问题.针对具有风险偏好的零售商,考虑了风险中性、风险厌恶和风险喜好三种态度,建立了由风险厌恶程度和悲观系数两个参数描述的基于条件风险值(CVaR)的集成目标决策函数.推导了不同风险偏好态度下的零售商最优订货决策,分析了不同风险偏好参数下的零售商订货决策变化情况.给出了能够完全协调风险偏好零售商和风险中性供应商的供应链回购契约协调机制.最后,进行了数值计算,验证了设计的供应链回购契约协调策略的有效性.结果表明,在给出的回购契约协调机制下,考虑风险偏好情况下的零售商最优订货决策能够保证整个供应链系统实现最优绩效,而供应链成员期望利润却随不同的风险偏好参数而不同.     

基于CVaR准则的折扣回购策略双层风险决策

首先,引入条件风险值(CVaR)准则,作为风险厌恶型的供应商和零售商的决策准则,建立了基于条件风险值(CVaR)准则的折扣回购策略双层风险决策模型.然后,导出了零售商在批发价格下的最优订购公式,证明了订购量随着折扣增大而增大,随着批发价格增大而减小,数值实验表明供应商可以通过折扣和批发价来分担零售商的风险损失,来使供应链达到协调.     

Quality investment and price decision in a risk-averse supply chain

In this paper, we investigate quality investment and price decision of a make-to-order (MTO) supply chain with uncertain demand in international trade. Due to volatility of orders from buyers, the supplier and the manufacturer in the supply chain are subject to financial risk. In contrast to the general assumption that players in a supply chain are risk neutral in quality investment and price decision, we consider the risk-averse behavior of the players in three different supply chain strategies: Vertical Integration (VI), Manufacturer’s Stackelberg (MS) and Supplier’s Stackelberg (SS). The study shows that both supply chain strategy and risk-averse behavior have significant impacts on quality investment and pricing. Compared to a risk-neutral supply chain, a risk-averse supply chain has lower, same and higher quality of products in VI, MS and SS, respectively. Also, we derive the conditions under which the supply chain strategy is implemented in a decentralized setting. A numerical study is used to illustrate some related issues.     

期末二次订购下风险规避且促销的收益共享契约协调研究

在期末二次订购下,利用CVaR准则考察收益共享下销售商风险规避且促销的决策问题,并得到一些有意义的管理启示。讨论了风险中性制造商在两生产模式下的生产决策。探讨了收益共享措施的协调问题,分析了各参数的关系,获得如下启示:销售商越是风险规避,首次订购量越少;制造商的首次生产量不一定是首次订购量,在有二次订货情况下可以投机生产来获得额外利润;在收益共享措施下,批发价固定,要风险态度不同的销售商订购等量的商品,风险规避度大的销售商,分享收益的比例小;如果制造商想要收益共享比例增大,那么首次批发价就要降低。     

反S型权重风险偏好对一类两级供应链的影响

大量实证研究表明,人们在不确定条件下,总是倾向于高估小概率事件并低估大概率事件,呈现反型权重风险偏好的特点。本文针对一类常见的由单供应商和单零售商组成的两级供应链,其中供应商有随机产出风险,分别考察了供应商与零售商的风险态度对其决策的影响。通过构建斯坦伯格博弈模型分析了供需双方的最优订购量和最优计划生产量。结果表明,供需双方或一方有反型风险态度时,保证供需双方均有激励动机签订契约的前提下,分散决策供应链的效率可达到集中决策的效果,也即供应链有可能达到协调。     

The value of rolling-horizon policies for risk-averse hydro-thermal planning

We consider the optimal management of a hydro-thermal power system in the mid and long terms. From the optimization point of view, this amounts to a large-scale multistage stochastic linear program, often solved by combining sampling with decomposition algorithms, like stochastic dual dynamic programming. Such methodologies, however, may entail prohibitive computational time, especially when applied to a risk-averse formulation of the problem. We propose instead a risk-averse rolling-horizon policy that is nonanticipative, feasible, and time consistent. The policy is obtained by solving a sequence of risk-averse problems with deterministic constraints for the current time step and future chance and CVaR constraints.The considered hydro-thermal model takes into account losses resulting from run-of-river plants efficiencies as well as uncertain demand and streamflows. Constraints aim at satisfying demand while keeping reservoir levels above minzones almost surely. We show that if the problem uncertainty is represented by a periodic autoregressive stochastic process with lag one, then the probabilistic constraints can be computed explicitly. As a result, each one of the aforementioned risk-averse problems is a medium-size linear program, easy to solve.For a real-life power system we compare our approach with three alternative policies. Namely, a robust nonrolling-horizon policy and two risk-neutral policies obtained by stochastic dual dynamic programming, implemented in nonrolling- and rolling-horizon modes, respectively. Our numerical assessment confirms the superiority of the risk-averse rolling-horizon policy that yields comparable average indicators, but with reduced volatility and with substantially less computational effort.     

A benchmark solution for the risk-averse newsvendor problem

In this paper, we derive the first order conditions for optimality for the problem of a risk-averse expected-utility maximizer newsvendor. We use these conditions to solve a special case where the utility function is any increasing differentiable function, and the random demand is uniformly distributed. This special case has a simple closed form solution and therefore it provides an insightful and practical interpretation to the optimal point. We show some properties of the solution and also demonstrate how it can be used for assessing the newsvendor utility function parameters.     

基于风险厌恶的下游供应链转运问题研究

当需求面临较大不确定性并且供货周期很长的情况下,转运策略成为提高供应链效率的重要解决方案。本文以条件风险价值（Conditional Value—at—Risk,简称CVaR）为风险度量准则,定量地研究了集中决策下的两级供应链系统的转运问题。我们得出了下游批发商的最优订货决策主要依赖于需求分布、单位缺货成本和风险厌恶程度等因素的一般性结论,并得出了均衡最优订货组合所需要满足的条件,重点分析了当需求基于均匀分布时,单位缺货成本和风险厌恶程度对最优订货组合的影响。     

基于CVaR测度和期权市场化定价的供应链协调研究

本文基于条件风险值(CVaR)和期权市场化定价规则,研究了具有风险规避特性的销售商和风险中性的供应商组成的供应链系统的协调问题。首先,利用CVaR风险测度工具建立了包含风险厌恶系数的销售商目标函数,得出了满足供应链协调的期权参数之间的关系。之后又根据Black-Schoels(B-S)模型得到满足市场化定价规则的期权参数之间的关系。通过联立上述两个条件证明了存在既满足供应链协调条件又满足期权市场化定价规则的期权定价组合(o^*,e^*),说明满足市场化定价规则的的期权契约能很好地协调风险规避型供应链。另外,文章还分析了模型中主要参数对该期权定价组合以及供应链各方利润的影响。最后,以数值分析的方式探讨了各参数实际对供应链系统运作效率的影响程度。     

Currency Denomination in Long-Term Debt Financing and Refinancing: A Cross- Hedging Paradigm

Under conditions of chronic exchange rate overshooting and mildly segmented capital markets, optimal currency denomination decision rules for international debt financing are derived for risk-neutral and risk-averse borrowers. For the latter, an inter-temporal expected utility framework yields the risk-adjusted cost of foreign debt, which allows for the pricing of currency cross-hedging effects in multi-currency debt portfolios, artificial currency unit-denominated debt instruments as well as currency swaps.     

Would a risk-averse newsvendor order less at a higher selling price?

We model a risk-averse newsvendor’s decision-making behavior with some commonly used classes of utility functions within the expected utility theory (EUT) framework. Under fairly general conditions of EUT, we show that a risk-averse newsvendor will order less than an arbitrarily small quantity as selling price gets larger if price is higher than a threshold value, i.e., the optimal order quantity decreases as the selling price increases.     

需求可变性降低对均值CVaR约束销售努力决策库存系统的影响

本文运用Levy提出的变换研究需求可变性降低对风险偏好零售商的库存决策、销售努力决策和期望效用的影响,用均值CVaR刻画零售商的风险偏好特性,它包括风险厌恶、风险追求,也具有损失规避的特性。首先,运用该变换定量刻画需求可变性的降低,证明该变换蕴含经典随机占优中的割准则序和二阶随机占优等。其次,给出系统的最优订货量、最优期望效用和最优销售努力水平,得到它们关于风险偏好系数的单调性,并给出降低需求可变性对期望效用的影响。第三,针对风险中性、风险厌恶(最大化CVaR)和风险追求(最小化CVaR)这三种特殊情况得到相应的结果,并给出企业在库存决策和促销决策的管理启示。最后,通过数值例子验证了得到的研究结果并给出相应的管理启示。