the multi item single period problem with an initial stock of convertible units abstract this paper deals with the situation of a number of end items each facing uncertain demand in a single period of interest besides being able to purchase units of the end items there is also available a stock of units that can be converted into end items but at unit costs that depend on the specific end item efficient solution procedures are presented for two situations i where the end item demand distributions are assumed known illustrated for the case of normally distributed demand and ii a distribution free approach where only the first two moments of the distributions are assumed known computational results for a set of problems are presented

employment adjustment versus hours adjustment is job security desirable firms can adjust to shocks by laying off and hiring workers or by adjusting the hours worked by each worker adjustment of hours provides job security for employed workers adjustment of employment generates higher labor market turnover and thus better job prospects for the unemployed since high turnover lowers the expected cost of being laid off by reducing the expected duration of unemployment there is a strategic complementarity between firms in the provision of job security this gives the possibility of multiple equilibria with different amounts of turnover copyright 1995 by the london school of economics and political science

analytical evaluation of lead time demand in polytree supply chains with uncertain demand lead time and inter demand time abstract in a stochastic supply chain network knowing the exact distribution of lead time demand ltd for each node allows determining inventory policy parameters service levels and optimal costs to determine the ltd distributions a stochastic analytical model has been developed for a multi echelon supply chain organised into an arbitrary polytree network where the variables demand quantity lead time and inter demand time are uncertain and can follow any probability distribution the model is based on a conventional nq batch policy for each node with discrete time and continuous demand any network can be broken down into four basic elements which represent root and leaf node topologies the model derives key convolutions for the four basic elements and then follows the same technique for evaluating resulting ltd distributions for each node in the network the paper presents the formulation in seven steps that can be used to obtain exact ltd distributions either in the two dimensional form or as a compound one dimensional ltd distribution per variable lead time for each node in any polytree supply chain the ltd distributions can be calculated either analytically for smaller networks or using numerical integration for larger networks the validation of the developed framework has been conducted by comparing the obtained formalism based ltd distribution for two test networks against simulation the pairs of simulated and formalism based distributions have been plotted against each other as well as subjected to various goodness of fit tests and error analysis the results suggest that the formalism based and simulated probability distributions are consistent

how much demand should be fulfilled we study the inventory replenishment of a product whose demand can be manipulated by restricting the supply this research is motivated by a novel marketing tactic employed by manufacturers of fashion and luxury items such a tactic combines innovative marketing with deliberate understocking in an attempt to create shortages i e waitlists that add to the allure and sense of exclusivity of a product and stimulate its demand we model the problem as a finite horizon periodic review system where demand in each period is a decreasing function of the net ending inventory in the previous period although the optimal structure can be complex in general under certain conditions we are able to characterize the optimal policy as a state dependent monotone base stock policy we compare this policy with the optimal policy for the case in which demand is independent of the net inventory we also show that understocking is optimal in various scenarios we then propose a novel strategy called the inventory withholding strategy to further explore the wait list effect by making customers wait even when there is inventory on hand to satisfy them our numerical experiments study the impact of various model parameters in combination with the wait list effect on the optimal policy and the corresponding expected profits

computing the non stationary replenishment cycle inventory policy under stochastic supplier lead times in this paper we address the general multi period production inventory problem with non stationary stochastic demand and supplier lead time under service level constraints a replenishment cycle policy r n s n is modeled where r n is the n th replenishment cycle length and s n is the respective order up to level we propose a stochastic constraint programming approach for computing the optimal policy parameters in order to do so a dedicated global chance constraint and the respective filtering algorithm that enforce the required service level are presented our numerical examples show that a stochastic supplier lead time significantly affects the structure of the optimal policy with respect to the case in which the lead time is assumed to be deterministic or absent

pricing and the news vendor problem a review with extensions in the newsvendor problem a decision maker facing random demand for a perishable product decides how much of it to stock for a single selling period this simple problem with its intuitively appealing solution is a crucial building block of stochastic inventory theory which comprises a vast literature focusing on operational efficiency typically in this literature market parameters such as demand and selling price are exogenous however incorporating these factors into the mode l can provide an excellent vehicle for examining how operational problems interact with marketing issues to influence decision making at the firm level in this paper we examine an extension of the newsvendor problem in which stocking quantity and selling price are set simultaneously we provide a comprehensive review that synthesizes existing results for the single period problem and develop additional results to enrich the existing knowledge base we also review and develop insight into a dynamic inventory extension of this problem and motivate the applicability of such models

evaluating the robustness of lead time demand models abstract this paper examines the robustness of lead time demand models for the continuous review r q inventory policy a number of classic distributions e g normal lognormal gamma poisson and negative binomial as well as distribution selection rules are examined under a wide variety of demand conditions first the models are compared to each other by assuming a known demand process and evaluating the errors associated with using a different model then the models are examined using a large sample of simulated demand conditions approximation results of inventory performance measures ready rate expected number of backorders and on hand inventory levels are reported results indicate that distribution selection rules have great potential for modeling the lead time demand

supply chain coordination for the joint determination of order quantity and reorder point using credit option abstract decisions regarding order quantity and reorder point are two major challenges in supply chain inventory management in this paper a coordination model of the joint determination of these two decision variables is proposed a decentralized supply chain consisting of one buyer and one supplier in a multi period setting is investigated demand and lead times are uncertain in our model an incentive scheme based on credit option has been developed to encourage the buyer to participate in the coordination model in this model the downstream member has the option of using credit to purchase goods during the credit time subject to its commitment to a jointly agreed order quantity and reorder point the credit time is determined in such a way that the two parties have incentives to participate the proposed incentive scheme can share the benefits of coordination between the two members based on their bargaining power the proposed model shows that the coordination of the reorder point together with order quantity can increase the overall chain profitability as well as each member s profitability

leadtime reduction in a q r inventory system an agency perspective abstract we examine the problem of designing and implementing a continuous review q r inventory system from an agency perspective in which the agent s effort influences the item s replenishment leadtime our results are as follows if the agent is risk neutral a linear or quadratic contract achieves first best for a risk averse agent with an exponential utility function assuming a normal leadtime distribution we determine the optimal linear contract extensive numerical experiments suggest that ignoring the possible influence of the agent on the replenishment leadtime can be costly but that the cost penalty of ignoring agency can be significantly reduced by a simple contract

a review of trade credit literature opportunities for research in operations abstract trade credit arises when a buyer delays payment for purchased goods or services its nature has predominantly been an area of inquiry for researchers from the disciplines of finance marketing and economics but it has received relatively little attention in other domains in our article we provide an integrative review of the existing literature and discuss conflicting study outcomes we organize the relevant literature into seven areas of inquiry and analyze four in detail trade credit motives order quantity decisions credit term decisions and settlement period decisions additionally we derive a detailed agenda for future research in these areas

modeling the experimentally organized economy complex dynamics in an empirical micro macro model of endogenous economic growth abstract the swedish micro to macro model moses is used to show how complex economic behavior emerges from interacting boundedly rational agents the simulation model has been calibrated using business firm data non linearities arise in its specification of technology the distribution of firm characteristics and in the rules that govern entry and exit the model economy is characterized by a restless competitive growth process that is normally robust but that now and then generates phases of local disorderly behavior including for some parameter settings the collapse of entire sectors the model explains why government agents have difficulty predicting the reactions of the economy to policies suggesting that government treads cautiously in order not to do more harm than good

inventory management for stochastic lead times with order crossovers we study the impact of stochastic lead times with order crossover on inventory costs and safety stocks in the order up to out policy to motivate our research we present global logistics data which violates the traditional assumption that lead time demand is normally distributed we also observe that order crossover is a common and important phenomenon in real supply chains we present a new method for determining the distribution of the number of open orders using this method we identify the distribution of inventory levels when orders and the work in process are correlated this correlation is present when demand is auto correlated demand forecasts are generated with non optimal methods or when certain ordering policies are present our method allows us to obtain exact safety stock requirements for the so called proportional order up to pout policy a popular implementable linear generalization of the out policy we highlight that the out replenishment policy is not cost optimal in global supply chains as we are able to demonstrate the pout policy always outperforms it under order cross over we show that unlike the constant lead time case minimum safety stocks and minimal inventory variance do not always lead to minimum costs under stochastic lead times with order crossover we also highlight an interesting side effect of minimizing inventory costs under stochastic lead times with order crossover with the pout policy an often significant reduction in the order variance

on the calculation of safety stocks when demand is forecasted the inventory control literature generally assumes that the demand distribution and all its parameters are known in practical applications it is often suggested to estimate the demand variance either directly or based on the one period ahead forecast errors the variance of the lead time demand essential for safety stock calculations is then obtained by multiplying the estimated per period demand variance by the length of the lead time however this is flawed since forecast errors for different periods of the lead time are positively correlated even if the demand process itself does not show process auto correlation as a result these traditional procedures lead to safety stocks that are too low this paper presents corrected lead time demand variance expressions and reorder levels for inventory systems with a constant lead time where demand fluctuates around a constant level firstly we derive the exact lead time forecast error of mean demand conditional on the true demand variance secondly we derive for normally distributed demand the correct reorder level under uncertainty of both the demand mean and variance we show how the results can be implemented in inventory models and particularly discuss batch ordering policies combined with moving average and exponential smoothing forecasts we find that traditional approaches can lead to safety stocks that are up to 30 percent too low and service levels that are up to 10 percent below the target

relief inventory modelling with stochastic lead time and demand the irregular demand and communication network disruption that are characteristics of situations demanding humanitarian logistics particularly after large scale earthquakes present a unique challenge for relief inventory modelling however there are few quantitative inventory models in humanitarian logistics and assumptions inherent in commercial logistics naturally have little applicability to humanitarian logistics this paper develops a humanitarian disaster relief inventory model that assumes a uniformly distributed function in both lead time and demand parameters which is appropriate considering the limited historical data on relief operation furthermore this paper presents different combinations of lead time and demand scenarios to demonstrate the variability of the model this is followed by the discussion of a case study wherein the decision variables are evaluated and sensitivity analysis is performed the results reveal the presence of a unique reorder level in the inventory wherever the order quantity is insensitive to some lead time demand values providing valuable direction for humanitarian relief planning efforts and future research

managing channel profits a channel of distribution consists of different channel members each having his own decision variables however each channel member s decisions do affect the other channel members profits and as a consequence actions a lack of coordination of these decisions can lead to undesirable consequences for example in the simple manufacturer retailer consumer channel uncoordinated and independent channel members decisions over margins result in a higher price paid by the consumer than if those decisions were coordinated in addition the ensuing suboptimal volume leads to lower profits for both the manufacturer and the retailer this paper explores the problems inherent in channel coordination we address the following questions what is the effect of channel coordination what causes a lack of coordination in the channel how difficult is it to achieve channel coordination what mechanisms exist which can achieve channel coordination what are the strengths and weaknesses of these mechanism what is the role of nonprice variables e g manufacturer advertising retailer shelf space in coordination does the lack of coordination affect normative implications from in store experimentation can quantity discounts be a coordination mechanism are some marketing practices actually disguised quantity discounts we review the literature and present a simple formulation illustrating the roots of the coordination problem we then derive the form of the quantity discount schedule that results in optimum channel profits this article was originally published in marketing science volume 2 issue 3 pages 239 272 in 1983

supply chain focus dependent supplier selection problem increasing globalization diversity of the product range and increasing customer awareness are making the market s highly competitive thereby forcing different supply chains to adapt to different stimuli on a continuous basis it is also well recognized that overall supply chain focus should be given an overriding priority over the individual goals of the players if one were to improve overall supply chain surplus among all the possible order winners cost and responsiveness seem to be the most significant metrics based on which majority of the supply chains compete with each other supplier selection problem is one of the crucial problems that need to be addressed in configuring a supply chain that could have far reaching ramifications on the total supply chain costs and order winnability our model that considers inventory costs and the supply chain cycle time reduction costs would aid a supply chain manager to make informed decisions with regard to supplier selection problem at any stage dependent upon the priorities attached to supply chain costs and cycle time inventory related costs and responsiveness related costs are the two primary cost elements that are considered in this model we are also making use of a novel dimensionless quantity called the coefficient of inverse responsiveness that not only facilitates the introduction of responsiveness related costs into the model but also improves the scalability and simplifies the analysis and interpretation of the results based on the strategic model developed we offer some very interesting managerial insights with respect to the effect of cost efficient operations and or location and cost of volume related flexibility at a stage on alternate suppliers which in turn affects the overall supply chain performance

inventory models with inventory level dependent demand a comprehensive review and unifying theory marketing researchers and practitioners have long recognized the demand of many retail items is proportional to the amount of inventory displayed recently two distinct types of inventory control models reflecting this relationship have appeared in the literature models in which the demand rate of an item is a function of the initial inventory level and those in which it is dependent on the instantaneous inventory level we present a comprehensive overview of this literature and demonstrate the equivalence of the two types of models through the use of a simple periodic review model an alternative approach to sensitivity analysis for inventory models with inventory level dependent demand is also presented

accurate lead time demand modeling and optimal inventory policies in continuous review systems abstract to construct an accurate probability density function for lead time demand in inventory management models a mixture of polynomials mops distributions is estimated using b spline functions from empirical data on demand per unit time this is accomplished by summarizing the empirical observations into separate datasets for each lead time value a mixture distribution approach is then applied to model lead time demand in a continuous review inventory system inventory policies can be determined without knowledge of the underlying demand and or lead time distributions an improvement to a mixture distribution approach that models the lead time demand distribution with a mixture of truncated exponentials mtes distribution is also presented and the mop and mte techniques are compared both methods provide reasonable accuracy but the mop approach requires lower computational time to determine optimal inventory policies the mixture distribution approach is also compared with solutions calculated using optimization through simulation and by compiling a discrete empirical lead time demand distribution

the stabilizing effect of inventory in supply chains this paper presents a hierarchical model framework for the analysis of the stabilizing effect of inventories in multiechelon manufacturing distribution supply chains this framework is used to compare the variance of demand to the variance of replenishment orders at different echelons of the system e g retailer wholesaler empirical data and experience with management games suggest that in most industries inventory management policies can have a destabilizing effect by increasing the volatility of demand as it passes up through the chain the bullwhip effect our model helps to explain these observations and indicates mechanisms that can promote stabilization the analysis results also define sufficient conditions for the existence of stabilization and relate these conditions to the optimality of myopic control policies

analysis of the impact of price sensitivity factors on the returns policy in coordinating supply chain this paper analyzes the impact of price sensitivity factors on characteristics of returns policy contracts in a single period product supply chain the contract considers stochastic and price dependent demand we present an analytical model and then use numerical methods with the stackelberg game to identify the contract properties we numerically show that a returns policy indeed improves supply chain performance however the benefits earned from the returns policy under price sensitive and variable demand are different for different supply chain partners first when price sensitivity is high profit of the manufacturer decreases with increase in demand variability second when price sensitivity is sufficiently high and demand variability increases the manufacturer has to surrender part of the profits to the retailer in order to continue sales however even after surrendering part of the profits to the retailer the manufacturer still earns profits that are higher than those available in a wholesale price contract last from the perspective of division of channel profits the retailer is always worse off in case of returns policies than in a wholesale price contract therefore to apply this form of incentive in practice managements should consider the impact of price sensitivity on the returns policy and its performance

stock wars inventory competition in a two echelon supply chain with multiple retailers this paper studies the competitive and cooperative selection of inventory policies in a two echelon supply chain with one supplier andn retailers stochastic demand is monitored continuously retailers incur inventory holding and backorder penalty costs the supplier incurs holding costs for its inventory and backorder penalty costs for backorders at the retailers the latter cost reflects the supplier s desire to maintain adequate availability of its product to consumers previous research finds the supply chain cost minimizing reorder point policies the cooperative solution the competitive solution is a nash equilibrium a set of reorder points such that no firm can deviate from the equilibrium and lower its cost it is shown that nash equilibria exist and a method is presented to find all of them in some settings the cooperative solution is a nash equilibrium competition does not necessarily lead to supply chain inefficiency in other settings competition leads to costs that are substantially higher than optimal usually but not always the competitive supply chain carries too little inventory three cooperation strategies are discussed change incentives change equilibrium and change control a set of contracts is provided that changes the firms incentives so that the optimal policy is a nash equilibrium an equilibrium change can improve performance but does not guarantee optimal performance to change control the firms let the supplier choose all reorder points a key component in vendor managed inventory that change leads to optimal supply chain performance

the effect of discrimination and of industry segmentation on japanese wage differentials in relation to education abstract the paper investigates japanese wage differentials based on the concept of industrial division the labor market is examined for two sectors separately namely competitive sectors and non competitive sectors the effects of female male difference of human capital and of occupation also are examined and the cost of discrimination is estimated by applying several quantitative methods it was found that worker characteristics such as education length of service and age were treated differently by sector sex and occupation also wage differentials by sex were mostly rooted in differential treatment of worker characteristics while wage differentials by sector were explained largely by firm size component the above general results however are greatly modified by workers occupations and industrial divisions

integrated safety stock optimization for multiple sourced stockpoints facing variable demand and lead time abstract the safety stock placement problem of a multi stage supply chain comprising multiple sourced stockpoints is addressed in this paper each stockpoint faces variability in its downstream demand and suppliers lead time the maximum among these suppliers lead time is determined by employing concepts of order statistics it is required to find the fill rate and safety stocks at each stockpoint that leads to satisfying the end customer service level at minimum safety stock placement cost hence the fill rates and the safety amounts are decided from a global supply chain perspective two models are proposed a decentralized safety stock placement model and a centralized consolidation model the decentralized model finds the safety amounts at each stockpoint required to face its underlying lead time demand variability the consolidation model finds the consolidated safety amounts that will be kept in the relevant consolidation center at each stage a benders decomposition technique is developed to handle the nonlinearity and binary restrictions involved in the safety stock consolidation model strategies proposed by the consolidation model achieve 45 2 62 reduction in safety amounts that results in a cost savings ranging between 22 2 44 2 as compared to the strategies proposed by the decentralized model

trends in unemployment wages and productivity the case of japan along with the high savings ratio the functioning of the labour market is one of the most important factors behind the macroeconomic performance of the postwar japan which foreign observers have christened the miracle of the rising sun in the first place the nature of the japanese labour market is important for the long run trend of japanese economic growth because labour and its quality are crucial factors for economic development the high quality of a well disciplined workforce as well as the migration of labour from rural to urban areas has contributed much to the rapid growth of the japanese economy second the nature of the labour market has influenced the pattern of japanese business cycles by buffering demand fluctuations the slow response of firms demand for labour combined with the fast response of the labour force participation ratio has prevented a sharp increase in the unemployment rate during recessions relatively flexible nominal and real wages have also enabled the japanese economy to adjust quite smoothly to supply shocks notably after the second oil crisis in this paper we shall review trends in unemployment wages and productivity in the postwar japanese economy and relate them to its macroeconomic performance we shall also summarize the current literature concerning features of the labour market evaluate quantitative estimates of trends in labour statistics and explore future prospects

a quantity discount approach to supply chain coordination abstract quantity discounts provide a practical foundation for inventory coordination in supply chains however typical supply chain participants may encounter difficulties in implementing the coordination policy simply because 1 specified lot size adjustments may deviate from the economic lot sizes and 2 the buying firm may face amplified overstocking risks related to increased order quantities the main objective of this study is to develop a quantity discount model that resolves the practical challenges associated with implementing quantity discount policies for supply chain coordination between a supplier and a buyer the proposed buyer s risk adjustment b ra model allows the supplier to offer discounts that capitalize on the original economic lot sizes and share the buyer s risk of temporary overstocking under uncertain demand the analytical results suggest that the proposed b ra discount approach is a feasible alternative for supply chain coordination under uncertain demand conditions

determining safety stock in the presence of stochastic lead time and demand we consider the problem of setting safety stock when both the demand in a period and the lead time are random variables there are two cases to consider in the first case the parameters of the demand and lead time distributions are known in the second case they are unknown and must be estimated for the case of known parameters a standard procedure is presented in the literature in this paper examples are used to show that this procedure can yield results that are far from the desired result a correct procedure is presented when the parameters are unknown it is assumed that a simple exponential smoothing model is used to generate estimates of demand in each period and that a discrete distribution of the lead time can be developed from historical data a correct procedure for setting safety stocks that is based on these two inputs is given for two popular demand models the approach is easily generalized to other models of demand safety stock calculation is simplified when certain normality assumptions are valid simulation results in the appendix indicate when these assumptions about normality are reasonable

coordination mechanisms of supply chain systems supply chain management scm has become an important management paradigm as supply chain members are often separate and independent economic entities a key issue in scm is to develop mechanisms that can align their objectives and coordinate their activities so as to optimize system performance in this paper we provide a review of coordination mechanisms of supply chain systems in a framework that is based on supply chain decision structure and nature of demand this framework highlights the behavioral aspects and information need in the coordination of a supply chain the identification of these issues points out several directions of future research in this area

coordination and profit sharing between a manufacturer and a buyer with target profit under credit option several studies have focused on buyer vendor coordination through quantity discount credit option mechanism but few quantitative models and investigations are available that have explored the mechanism for transfer of surplus generated due to coordination in this paper we develop a coordination mechanism through credit option such that both the parties can divide the surplus equitably after satisfying their own profit targets two situations are explored here in the first situation both the parties have no individual profit target from the business whereas in the second situation there are individual profit target for both the parties the proposed mechanism for division of surplus is studied through a numerical study and the impact of different parameter values on the results are examined

competitive and cooperative inventory policies in a two stage supply chain we investigate a two stage serial supply chain with stationary stochastic demand and fixed transportation times inventory holding costs are charged at each stage and each stage may incur a consumer backorder penalty cost e g the upper stage the supplier may dislike backorders at the lower stage the retailer we consider two games in both the stages independently choose base stock policies to minimize their costs the games differ in how the firms track their inventory levels in one the firms are committed to tracking echelon inventory in the other they track local inventory we compare the policies chosen under this competitive regime to those selected to minimize total supply chain costs i e the optimal solution we show that the games nearly always have a unique nash equilibrium and it differs from the optimal solution hence competition reduces efficiency furthermore the two games equilibria are different so the tracking method influences strategic behavior we show that the system optimal solution can be achieved as a nash equilibrium using simple linear transfer payments the value of cooperation is context specific in some settings competition increases total cost by only a fraction of a percent whereas in other settings the cost increase is enormous we also discuss stackelberg equilibria

optimal safety stock levels of subassemblies and manufacturing components abstract in order to control the time to market and manufacturing costs companies produce and purchase many parts and components before receiving customer orders consequently demand forecasting is a critical decision process using modular product design and super bills of materials are two effective strategies for developing a reliable demand forecasting process they reduce the probability of stockouts in diversified production contexts furthermore managing and controlling safety stocks for pre assembled modules provide an effective solution to the problem of minimizing the effects of forecast errors this paper develops evaluates and applies innovative cost based analytical models so that the optimal safety stock of modular subassemblies and components in assembly to order and manufacturing to order systems respectively can be rapidly quantified the implementation of the proposed models in two industrial case applications demonstrates that they significantly reduce the safety stock inventory levels and the global logistical cost

integrated vendor buyer cooperative models with stochastic demand in controllable lead time abstract this article presents the single vendor single buyer integrated production inventory models we relax the assumption that lead time demand x is deterministic and assume that it is stochastic also we assume that shortage during the lead time is permitted and lead time can be reduced at an added cost two models are considered here in the first model the demand of lead time follows a normal distribution and in the second model it is distribution free for both cases we develop effective iterative procedures for finding the optimal policy and numerical examples are used to illustrate the benefits of integration

robust inventory decision under distribution uncertainty a cvar based optimization approach abstract we study the robust inventory decision making problem faced by risk averse managers with incomplete demand information in a newsvendor setting three basic models are developed expected profit maximization cvar based profit maximization and a combination of the two each model is robustly formulated under the assumption of ellipsoid discrete distribution and again under the box discrete distribution each robust model can be mathematically transformed into a second order cone program for ellipsoid uncertainty or into a general convex optimization problem for box uncertainty both transformed problems can be optimally solved directly we offer propositions with proof to show the equivalence of the transformed problems with the original ones numerical examples are given to validate the proposed approach we find that the performances under both ellipsoid and box uncertain distributions are robust finally sensitivity analysis with respect to risk averse levels and trade off coefficients is conducted to validate the proposed models and solution approaches

an analysis of trends in female labor force participation in japan until recently the aggregate female labor force participation rate in japan has shown a secular declining trend throughout the postwar period of economic development participation of paid female employees alone exhibits a steadily rising trend more or less comparable to that in the united states and european countries although the fertility rate dropped drastically shortly after world war ii in the subsequent period increases in female education and a relative improvement of female wages appear to have promoted a substantial increase in paid female employment labor supply equations for paid employees estimated from time series data provide negative income and positive wage elasticities cross sectional analysis gives reasonable results particularly for middle age wives absolute values of estimated wage elasticity notably have almost always been smaller than income elasticity unlike many research findings in the united states

integrated vendor buyer cooperative inventory models with variant permissible delay in payments abstract the integrated inventory models usually have the advantage of reducing total cost however the way to allocate the cost savings from the integration to the buyer and vendor is critical to the success of the joint relationship between both sides to deal with this problem this paper develops the integrated models with the permissible delay in payments for determining the optimal replenishment time interval and replenishment frequency applying the models and considering the coefficient of negotiation and the maximum delay payment period a simple solution algorithm is presented to resolve the allocation of cost savings in the integration model the coefficient of negotiation is adopted to determine the compromise between the buyer s and vendor s cost savings a numerical example is used to demonstrate the feasibility of the proposed integration models a sensitivity analysis is also conducted to demonstrate some properties using the information from the proposed models the buyer and vendor can achieve an acceptable compromise solution for both sides in the supply chain management

unemployment insurance and short time compensation the effects on layoffs hours per worker and wages we analyze two unemployment insurance systems in one unemployed workers receive benefits while those on reduced hours do not as in north america at least until recently in the other short time compensation is paid to workers on reduced hours as in europe the first system causes inefficient temporary layoffs for some parameters the latter does not but implies inefficient hours per worker some evidence is presented regarding these effects despite policymakers recent enthusiasm for short time compensation the clear implication of this project is that changes should come on the tax not benefit side of the system

benefits of leadtime information and of its combination with demand forecast information abstract this paper studies both the benefits of leadtime information and the interrelationships among demand forecast information leadtime uncertainty and leadtime information for improving inventory control performance to this end it explicitly incorporates both leadtime information and demand forecast information into an inventory model although they have conventionally been dealt with individually in the literature specifically it considers a periodic review inventory model with uncertain leadtimes in which both leadtime information and demand forecast information are available the leadtime information is modeled as the information of the arrival of outstanding orders and the demand forecast information as the martingale model of forecast evolution mmfe the paper analyzes the way to use both leadtime information and demand forecast information for inventory control operations specifically under certain conditions the optimality of the state dependent base stock policy is shown and an effective heuristic policy is developed it also derives some managerial insights for exploiting both leadtime information and demand forecast information in the case where leadtimes are uncertain for instance while leadtime information itself significantly improves inventory control performance it also enhances the benefits of demand forecast information specifically the benefits of demand forecast information may significantly decrease as leadtime uncertainty increases however the decrease of the benefits of demand forecast information may be alleviated with leadtime information

improved quality setup cost reduction and variable backorder costs in an imperfect production process abstract this paper illustrates the relationship between quality improvement reorder point and lead time as affected by backorder rate in an imperfect production process to reduce the total system cost by optimizing the setup cost lot size lead time reorder point and process quality parameter simultaneously we first consider that the lead time demand follows a normal distribution then we apply the distribution free approach for the lead time demand we prove two lemmas which are used to find optimal solutions for the basic and distribution free models we compare our models with the existing models using numerical examples and show that significant savings over the existing models can be achieved

the strategic use of capacity slack in the economic lot scheduling problem with random demand growing interest in designing systems with capacity slack as one form of flexibility raises many questions about its use and its usefulness in the framework of the economic lot scheduling problem with stochastic demand we develop on optimization based model that considers capacity slack safety stock and overtime explicitly and has the objective of minimizing the expected cost per unit time of inventory overtime and where applicable setup costs the solution is a continuous time production plan that consists of a time dependent inventory trajectory for each of the parts including the placement of planned idle time in the schedule we consider schedule stability to be desirable because of potential effects on upstream and downstream operations in multistage production settings thus the plan also has certain characteristics that contribute to achieving stability our results on the relative merits of capacity slack and safety stock indicate that capacity slack in the form of planned idle time is

from plan to markets abstract while formerly planned economies lack critical institutions ailing welfare economies have too many reducing investment incentives in both while institutional redesign is urgent in the formerly planned economies there is no instant concern in the west where institutional change must be realized through reluctant democratic procedures some formerly planned economies therefore are likely to improve upon the west in institutional design and experience superior long run economic growth they explicitly link investment incentives one way to property rights and the other to investment and growth to demonstrate how such superior performance can be achieved

an optimal vendor buyer cooperative policy under generalized lead time distribution with penalty cost for delivery lateness abstract this paper presents an integrated inventory model for a single vendor and single buyer where lead time is a stochastic variable with general distribution function the vendor delivers goods at a fixed lot size to the buyer who has a constant demand rate storage is permitted on both parties but a penalty cost is assessed when the vendor delivers the shipment late beyond a threshold time the problem is formulated as a nonlinear cost model which needs to be minimized to arrive at an optimal policy for reorder point order quantity and number of shipments from the vendor to buyer to cooperatively operate the joint contract the solution procedure involves both closed form solution and iterative search procedure for this multi dimensional problem numerical examples are presented for uniform exponential and normally distributed lead time s to demonstrate the solution methodology as well as a precursor test for special cases the model presented here are applicable for numerous two stage supply chain systems including retail businesses assembly and production houses where two parties of the supply chain are tied to their common goal of achieving minimum total cost of inventory operation

an easy derivation of the order level optimality condition for inventory systems with backordering we analyze the classical inventory model with backordering where the inventory position is controlled by an order level order quantity policy the cost for a backorder contains a fixed and a time proportional component demand can be driven by any discrete process order lead times may be stochastic and orders are allowed to cross the optimality condition for the order level given some predetermined order quantity is derived using an easy and insightful marginal cost analysis it is further shown how this condition can easily be approximately rewritten in well known forms for special cases

coordination of social responsibility and order quantity in a two echelon supply chain a collaborative decision making perspective abstract regarding globalization growing trend and sustainability concerns the need for paying attention to the issues of corporate social responsibility csr not only applies to individual firms but also extends to the whole supply chain sc networks assisting csr issues in one individual firm will thoroughly influence other supply chain members in this paper a supplier retailer sc is considered in a newsvendor setting it is possible for the supplier to invest in csr activities which could improve the popularity of products and subsequently market demand firstly both members decisions under decentralized and centralized decision making models are investigated afterwards a novel collaborative model is proposed to determine optimal order quantity and csr investment thus maximizing the whole sc profits and also motivating members to participate finally the results of decentralized centralized and collaborative models are compared and some managerial insights are provided numerical experiments indicate that under some circumstances alongside the increment of sc profits more csr investment and better csr performance level will be achieved through the collaborative model than other decision making structures

the relationship between production and unemployment in japan okun s law in comparative perspective abstract this paper studies the question whether the celebrated okun s law a relation between excess capacity and unemployment applies to the postwar japanese economy though the fitness of estimation is weak the coefficient that measures the responsiveness of the output gap to the unemployment rate is very large reaching 28 this large coefficient can be attributed to the elastic response in the female participation ratio to flexible working hours to the slow adjustment in employment and to changes in industrial structures the results are compared with those in the united states

the inventory billboard effect on the lead time decision abstract this research brings together two important research streams lead time management and the inventory billboard effect while traditional inventory theory which assumes that demand is independent of the average on hand inventory recommends that lead time be reduced to the lowest level possible it is clearly not the case when inventory exhibits the billboard effect which refers to the demand stimulating effect of inventory we use analytical models to examine the firm s optimal lead time decision in the presence of the inventory billboard effect in two scenarios with and without inventory based competition we begin with the single firm scenario where a firm employs the base stock policy for the infinite horizon continuous review inventory problem with a deterministic lead time and inventory dependent demand the firm s decisions are to choose the optimal lead time and the corresponding base stock level to maximize its expected profit rate we find that the inventory billboard effect favors a long lead time because a long lead time results in a higher inventory level which in turn induces more demand we then consider the case where two firms compete on inventory for customer demand we completely characterize the unique nash equilibrium and provide closed form solutions which allow us to conclude that inventory based competition pressures both firms to increase the lead time our numerical studies show that the extent to which demand depends on inventory amplify the impact of competition on the optimal decisions and the associated profit our findings suggest that lead time reduction although widely advocated by popular production philosophies such as just in time has to be carefully evaluated when inventory exhibits billboard effect

on optimal payment time for a retailer under permitted delay of payment by the wholesaler abstract jamal et al 2000 optimal payment time for a retailer under permitted delay of payment by the wholesaler international journal of production economics 66 59 66 study a wholesaler retailer supply chain where the retailer is given a permissible credit period to pay back the dues without paying any interest to the wholesaler the problem is modeled as a cost minimization problem with two decision variables the payment time p of the retailer and the length of the inventory cycle t while the model represents in general an interesting problem we show in this note that there are a number of nontrivial flaws contained in the development of their model and therefore the solution they derived is not correct we give the correct model and derive the corresponding optimal solution

minimax distribution free procedure with backorder price discount abstract the inventory models analyzed in this paper explore the problem in which the lead time and ordering cost reductions are inter dependent in the continuous review inventory model with backorder price discount the objective is to minimize total related cost by simultaneously optimizing the order quantity reorder point lead time and backorder price discount moreover we assume that the mean and variance of the lead time demand are known but its probability distribution is unknown we apply a minimax distribution free procedure to find the optimal solution and three numerical examples are given to illustrate the results

integration of capacity pricing and lead time decisions in a decentralized supply chain abstract we consider a decentralized supply chain consisting of a supplier and a retailer facing price and lead time sensitive demand the decision process is modelled by a stackelberg game where the supplier as a leader determines the capacity and the wholesale price and the retailer as a follower determines the sale price and lead time the equilibrium strategy of these two players is obtained by comparing with the performance of the corresponding decentralized chain without capacity decision as a benchmark we characterize the impact of capacity decision on the players profit i e the supplier s profit may be always significantly increased while the retailer s profit is only increased when the capacity is underestimated in the benchmark model further we demonstrate that the integration of capacity decision can also significantly reduce the profit loss caused by double marginalization finally we find that the revenue sharing and two part tariff contracts cannot coordinate the decentralized channel instead we propose a franchise contract with a contingent rebate that can achieve channel coordination and a win win outcome

single supplier multiple buyer supply chain coordination incorporating buyers expectations under vertical information sharing abstract we address the coordination problem in a single supplier multiple buyer supply chain the supplier wishes to coordinate the supply chain by offering quantity discounts to obtain their complete cost information the supplier exchanges his own cost parameters with buyers leading to vertical information sharing the supplier thinks that the buyers as they have access to supplier s setup and holding cost information may demand a portion of the anticipated coordination savings based on the partial information they hold about the cost structure of the entire supply chain we model each buyer s expectations based on her limited view of the entire supply chain which consists of herself and the supplier only these expectations are then incorporated into the modeling of the supply chain which results in a generalization of the traditional stackelberg type models we discuss alternative efficiency sharing mechanisms and propose methods to design the associated discount schemes that take buyers expectations into account in designing the discount schemes we consider both price discriminatory and non price discriminatory approaches the study adds to the existing body of work by incorporating buyers expectations into a constrained stackelberg structure and by achieving coordination without forcing buyers to explicitly comply with the supplier s replenishment period in choosing their order quantities the numerical analysis of the coordination efficiency and allocation of the net savings of the proposed discount schemes shows that the supplier is still able to coordinate the supply chain with high efficiency levels and retain a significant portion of the net savings

using the inventory theoretic framework to determine cost minimizing supply strategies in a stochastic setting abstract in a stochastic supply link between a supplier and a receiver a crucial component of the total logistics costs is formed by the costs of safety stock held by the receiver to protect against stockouts the level of safety stock depends on among other things the statistical distribution of demand during lead time ddlt for practical reasons ddlt is often assumed to be normally distributed however previous research has indicated that this assumption is often invalid in real life situations and that it can have a significant impact on safety stocks or service levels this paper first presents an extensive review of previous research on stochastic inventory models with specific emphasis on the distributions used to model period demand lead time and or ddlt the paper also discusses a real life case study in which the total logistics costs are calculated for a number of different transport modes for a gamma demand gamma lead time setting

wage rigidity and unemployment in oecd countries real wage rigidity is often blamed for causing unemployment in the wake of adverse real shocks like changes in productivity or the terms of trade likewise nominal wage rigidity is blamed for causing unemployment in the wake of adverse nominal shocks like falls in nominal demand 1 however there has been relatively little systematic discussion of how these concepts should be defined some authors e g sachs 1979 have defined real wage rigidity as the opposite of nominal wage rigidity with the us nominally rigid and europe really rigid 2 the rigidity of european real wages has then been used to explain why europe has experienced a greater increase in unemployment since 1973 than the us but in this discussion real wage rigidity has not been measured in a way which would in fact predict how much unemployment would result from a given real shock the discussion has focused on the degree of nominal inertia in the system but the unemployment cost of real shocks does not depend primarily on the degree of nominal inertia but rather on the effect of unemployment in the phillips curve

the effect of leadtime uncertainty in a simple stochastic inventory model we study a basic continuous time single item inventory model where demands form a compound poisson process and leadtimes are stochastic the performance measure of interest is the long run average cost order costs are linear so a base stock policy is optimal we focus on the behavior of the optimal base stock level in response to stochastically larger or more variable leadtimes we also investigate the behavior of the corresponding long run average costs we show that a stochastically larger leadtime requires a higher optimal base stock level however a stochastically larger leadtime may not necessarily result in a higher optimal average cost because sometimes the variability effects may dominate on the other hand a more variable leadtime always leads to a higher optimal average cost the effect of leadtime variability on optimal policies depends on the inventory cost structure a more variable leadtime requires a higher optimal base stock level if and only if the unit penalty holding cost rate is high low similar results regarding the effect of leadtime demand are also discussed in this latter case the compound poisson assumption is not necessary

implicit contracts a survey 7mplicit contracts resolve the distribution of uncertainty and utilization of specific human capital between risk averse workers and less risk averse firms incomplete contracts are required to yield involuntary layoffs in contract markets otherwise contracts are efficient and pareto optimal by construction there is a close relation between contract theory and neoclassical labor market theory contracts smooth consumption but increase the volatility of labor supply and labor utilization to demand disturbances because contractural insurance eliminates the income effects of socially diversifiable risks this result is similar to the intertemporal substitution hypothesis however the price mechanism in a contract is substantially different contracts embody a nonlinear two part pricing scheme the lump sum part allocates the income consumption consequences of risks and the marginal pricing part allocates production and labor utilization this implicit pricing mechanism is in all respects flexible though the observed average hourly wage combines both parts and may give the outward appearanceof rigidity furthermore the observed average wage rate in a contract does not reflect marginal conditions necessary for structural econometric estimation indivisibilities appear necessary to account for the split between work sharing and layoffs contracts with private information are also considered in the nonlinear pricing context this abstract was borrowed from another version of this item

the newsvendor problem review and directions for future research in this paper we review the contributions to date for analyzing the newsvendor problem our focus is on examining the specific extensions for analyzing this problem in the context of modeling customer demand supplier costs and the buyer risk profile more specifically we analyze the impact of market price marketing effort and stocking quantity on customer demand how supplier prices can serve as a coordination mechanism in a supply chain setting integrating alternative supplier pricing policies within the newsvendor framework and how the buyer s risk profile moderates the newsvendor order quantity decision for each of these areas we summarize the current literature and develop extensions finally we also propose directions for future research

evolution economic competence and the market for corporate control abstract to assess the merits of the market for corporate control this paper examines two processes which standard analysis does not study the allocation of economic competence and the evolution of organizational structures economic competence is seen to be an unusual scarce resource embodied in the very ways in which individuals and organizations take economic decisions which guides the allocation of all scarce resources including itself its efficient allocation is shown to require an evolutionary trial and error process where the market for corporate control plays a crucial role

measuring the impact of asymmetric demand distributions on inventories most studies on inventory management under demand uncertainty analyse the detrimental impacts of demand variability i e its coefficient of variation consequences of the shape of demand distribution i e its multi modality and asymmetry have instead received only minor attention this paper focuses on the study of the effects of the shape of demand distribution on inventories results from a simulation show that demand shape plays a key role in the determination of the stock investments in particular this paper measures asymmetry of demand distributions and shows its significant impact on inventories moreover it is demonstrated how multi modality and asymmetry can both have a negative or a positive impact depending on the type of asymmetry and the target service level the firm is facing

the returns to labour services in west german manufacturing industry production functions distinguishing between the stock and utilisation dimensions of factor labour and capital inputs are critically surveyed an extension to the existing literature is suggested whereby normal and overtime hours are separated within an appropriate non linear functional specification the econometric performance of this model is then compared with the main alternatives from the existing literature the empirical work is based on pooled cross section time series data which refer to west german manufacturing industries 1968 1978 estimates of the returns to labour services are also discussed in the light of related theoretical aspects of factor demand functions

channel coordination and quantity discounts this paper presents a model for analyzing the impact of joint decision policies on channel coordination in a system consisting of a supplier and a group of homogeneous buyers the joint decision policy characterized by the unit selling price and the order quantity is coordinated through quantity discounts and franchise fees both the annual demand rate and the operating cost including the purchase ordering and inventory holding costs depend on the joint decision policy employed this paper contributes by integrating work addressing quantity discounts on inventory and ordering policies and work focusing on the control mechanism provided by quantity discounts in channel coordination it is shown that the optimal all unit quantity discount policy is equivalent to the optimal incremental quantity discount policy in achieving channel coordination furthermore it is shown that quantity discounts alone are not sufficient to guarantee joint profit maximization the analyses of the general models are illustrated by specific analytical results obtained for a given demand function