the democratic political economy of progressive income taxation why do both left and right political parties typically propose progressive income taxation schemes in political competition analysis of this problem has been hindered by the two dimensionality of the issue space to give parties a choice over a domain that contains both progressive and regressive income tax policies requires an issue space that is at least two dimensional nash equilibrium in pure strategies of the standard two party game whose players have complete preferences over a two dimensional policy space generically fails to exist i introduce a new equilibrium concept for political games based on the fact of factional conflict within parties each party is supposed to consist of reformists militants and opportunists each faction has a complete preference order on policy space but together they can only agree on a partial order nash equilibria of the two party game where the policy space consists of all quadratic income tax functions and each party is represented by its partial order exist and it is shown that in such equilibria both parties propose progressive income taxation

a simple heuristic for joint inventory and pricing models with lead time and backorders we study a joint inventory and pricing problem in a single stage system with a positive lead time we consider both additive and multiplicative demand forms this problem is in general intractable due to its computational complexity we develop a simple heuristic that resolves this issue the heuristic involves a myopic pricing policy that generates each period s price as a function of the initial inventory level and a base stock policy for inventory replenishment in each period the firm monitors its so called price deflated inventory position and places an order to reach a target base stock level the price deflated inventory position weights the on hand and pipeline inventory according to a factor that reflects the sensitivity of price to the net inventory level to assess the effectiveness of our heuristic we construct an upper bound to the exact system the upper bound is based on an information relaxation approach and involves a penalty function derived from the proposed heuristic a numerical s

optimal policies for serial inventory systems under fill rate constraints a continuous review serial production distribution system with discrete compound poisson demand for the end product is considered unmet demand is back ordered production transportation times are constant all deliveries from one stage to the next must be multiples of given batch sizes we consider the problem of minimizing the holding costs under a fill rate constraint using recent results by chen 2000 we show that under a set of restricted but plausible assumptions the optimal policy is an echelon stock multistage r nq policy with one of the reorder points varying over time we provide a simple procedure for the determination of the optimal policy

joint management of capacity and inventory in make to stock production systems with multi class demand we evaluate the benefits of coordinating capacity and inventory decisions in a make to stock production environment we consider a firm that faces multi class demand and has additional capacity options that are temporary and randomly available we formulate the model as a markov decision process mdp and prove that a solution to the optimal joint control problem exists for several special cases we characterize the structure of the optimal policy for the general case however we show that the optimal policy is state dependent and in many instances non monotone and difficult to implement therefore we consider three pragmatic heuristic policies and assess their performance we show that the majority of the savings originate from the ability to dynamically adjust capacity and that a simple heuristic that can adjust production capacity based on workload fluctuation but uses a static production rationing policy can result in significant savings

volume flexibility in services the costs and benefits of flexible labor resources organizations can create volume flexibility the ability to increase capacity up or down to meet demand for a single service through the use of flexible labor resources e g part time and temporary workers as compared to full time workers although organizations are increasingly using these resources the relationship between flexible labor resources and financial performance has not been examined empirically in the service setting we use two years of archival data from 445 stores of a large retailer to study this relationship we hypothesize and find that increasing the labor mix of temporary or part time workers shows an inverted u shaped relationship with sales and profit while temporary labor mix has a u shaped relationship with expenses thus although flexible labor resources can create volume flexibility for a firm along multiple dimensions it is possible to have too much of a good thing this paper was accepted by serguei netessine operations management

a real options approach to labour shifts planning under different service level targets abstract firms that experience uncertainty in demand as well as challenging service levels face among other things the problem of managing employee shift numbers decisions regarding shift numbers often involve significant expansions or reductions in capacity in response to changes in demand in this paper we quantify the impact of treating shifts in workforce expansion as investments while considering required service level improvements the decision to increase shifts whether by employing temporary workers or hiring permanent employees is one that involves significant risks traditional theories typically consider reversible investments and thus do not capture the idiosyncrasies involved in shift management in which costs are not fully reversible in our study by using real options theory we quantify managers ability to consider this irreversibility aiming to enable them to make shift decisions under conditions of uncertainty with the maximum level of flexibility our model aims to help managers make more accurate decisions with regard to shift expansion under service level targets and to defer commitment until future uncertainties can be at least partially resolved overall our investigation contributes to studies on the time required to introduce labour shift changes while keeping the value of service level improvements in mind

production planning and pricing policy in a make to stock system with uncertain demand subject to machine breakdowns abstract we consider a make to stock system served by an unreliable machine that produces one type of product which is sold to customers at one of two possible prices depending on the inventory level at the time when a customer arrives i e the decision point the system manager must determine the production level and selling price at each decision point we first show that the optimal production and pricing policy is a threshold control which is characterized by three threshold parameters under both the long run discounted profit and long run average profit criteria we then establish the structural relationships among the three threshold parameters that production is off when inventory is above the threshold and that the optimal selling price should be low when inventory is above the threshold under the scenario where the machine is down or up finally we provide some numerical examples to illustrate the analytical results and gain additional insights

policy objectives and performance in a mixed market with bargaining abstract we analyse a mixed duopoly in which wages and salaries are determined by nash bargaining and where the public firm s unit costs depend on its objectives because of constant returns to scale welfare maximisation without restriction would eliminate or significantly weaken the private firm therefore we focus on constrained welfare maximisation in which case unit costs are normally higher in the public firm on the other hand the private firm may even earn more than in a monopoly if the public firm maximises profits or if the constraint offers too much protection

arab external investments relation to national wealth estimation and consequences abstract the purpose of the paper is to shed some light on the issue of repatriation of arab external investments we do that by first relating these investments to the concept of arab national wealth and then by providing estimates of their size and analyses of their consequences and factors affecting their home return the paper puts the total value of capital outflows from the arab countries during 1975 2000 at between us 212 and 323 billion the prime factor that not only could affect the home return of arab capital but also the attraction of foreign capital is higher risk adjusted marginal productivity of capital through improvements in the efficiency of arab investments the paper reaffirms that this could come about by diversification of the economic structure financial development political liberalization and a leading role for the private sector

serial supply chains with economies of scale bounds and approximations we consider two models of stochastic serial inventory systems with economies of scale for which the forms of optimal policies are known in the first model each stage has a fixed order quantity while in the second model there is a fixed order cost for external supplies for each model we show that the optimal policy parameters can be bounded and approximated by a series of independent single stage optimal policy parameters we further construct closed form bounds and approximations for the single stage solutions and apply them to the serial systems these results provide simple and effective solutions that will help to facilitate implementations in practice they also allow us to see the connections between the serial and single stage systems and sharpen our intuition on optimal policy parameters and system behavior

investment and capacity choice under uncertain demand this paper extends the real options literature by discussing an investment problem where a firm has to determine optimal investment timing and optimal capacity choice at the same time under conditions of irreversible investment expenditures and uncertainty in future demand after the project is installed with a certain maximum capacity this capacity is fixed as an upper boundary to the output and cannot be adjusted later on it turns out that in the framework of this once and for all decision uncertainty in future demand leads to an increase in optimal installed capacity but on the other hand it causes investment to be delayed to an extent that even small uncertainty makes waiting and accumulation of further information the optimal decision for large ranges of demand limiting the capacity which may be installed weakens this extreme effect of uncertainty

evaluating echelon stock r nq policies in serial production inventory systems with stochastic demand this paper studies echelon stock r nq policies in serial production inventory systems with stochastic demand we provide a recursive procedure to compute the steady state echelon inventory levels of the systems which can be used to evaluate the long run average holding and backorder costs as well as other performance measures the procedure is based upon an observation of a relationship between the inventory status of adjacent stages in a serial system we also device exact formulas for replenishment frequencies and setup costs our results apply to both continuous review systems with compound poisson demand and periodic review systems with independent identically distributed demands a preliminary numerical study was conducted to explore the cost effectiveness of echelon stock r nq policies for two stage systems with simple poisson demand we compared among the minimum costs of echelon stock r nq policies a lower bound on the minimum achievable costs and the minimum costs of installation stock r nq policies finally we present a modification of an existing approximate evaluation procedure

optimal policies and approximations for a serial multiechelon inventory system with time correlated demand since clark and scarf s pioneering work most advances in multiechelon inventory systems have been based on demand processes that are time independent this paper revisits the serial multiechelon inventory system of clark and scarf and develops three key results first we provide a simple lower bound approximation to the optimal echelon inventory levels and an upper bound to the total system cost for the basic model of clark and scarf second we show that the structure of the optimal stocking policy of clark and scarf holds under time correlated demand processes using a martingale model of forecast evolution third we extend the approximation to the time correlated demand process and study in particular for an autoregressive demand model the impact of lead times and autocorrelation on the performance of the serial inventory system

exact evaluation of batch ordering inventory policies in two echelon supply chains with periodic review this paper studies a two echelon supply chain with stochastic and discrete consumer demand batch order quantities periodic inventory review and deterministic transportation times reorder point policies manage inventories at every location average inventory backorders and fill rates are evaluated exactly for each location safety stock is evaluated exactly at the lower echelon and a good approximation is detailed for the upper echelon numerical data are presented to demonstrate the model s utility it is found that system costs generally increase substantially if the upper echelon is restricted to carry no inventory of if the upper echelon is required to provide a high fill rate in many cases it is optimal to set the upper echelon s reorder point to yield near zero safety stock yet in some cases this simple heuristic can significantly increase supply chain operating costs finally policies selected under the assumption of continuous inventory review can perform poorly if implemented in an environment with periodic review

integrated inventory model for deteriorating items under a multi echelon supply chain environment abstract as the industrial environment becomes more competitive supply chain management has become essential the objective of this research is to develop a multi echelon inventory model for a deteriorating item and to derive an optimal joint total cost from an integrated perspective among the supplier the producer and the buyer a computer code is developed to derive the optimal solution a numerical example is given to illustrate the model this paper shows that the integrated approach strategy results in the lowest joint total cost as compared with the independent decision approaches

integrated capacity and inventory management with capacity acquisition lead times we model a make to stock production system that utilizes permanent and contingent capacity to meet non stationary stochastic demand where a constant lead time is associated with the acquisition of contingent capacity we determine the structure of the optimal solution concerning both the operational decisions of integrated inventory and flexible capacity management and the tactical decision of determining the optimal permanent capacity level furthermore we show that the inventory either before or after production the pipeline contingent capacity the contingent capacity to be ordered and the permanent capacity are economic substitutes we also show that the stochastic demand variable and the optimal contingent capacity acquisition decisions are economic complements finally we perform numerical experiments to evaluate the value of utilizing contingent capacity and to study the effects of capacity acquisition lead time providing useful managerial insights

optimal policies for multiechelon inventory problems with markov modulated demand this paper considers a multistage serial inventory system with markov modulated demand random demand arises at stage 1 stage 1 orders from stage 2 etc and stage n orders from an outside supplier with unlimited stock the demand distribution in each period is determined by the current state of an exogenous markov chain excess demand is backlogged linear holding costs are incurred at every stage and linear backorder costs are incurred at stage 1 the ordering costs are also linear the objective is to minimize the long run average costs in the system the paper shows that the optimal policy is an echelon base stock policy with state dependent order up to levels an efficient algorithm is also provided for determining the optimal base stock levels the results can be extended to serial systems in which there is a fixed ordering cost at stage n and to assembly systems with linear ordering costs

optimal policy for a two stage assembly system under random demand this paper considers an inventory system in which an end product is assembled from two components each of which is ordered from an external supplier only the end product has final demand which is assumed to be random using the functional equation approach of dynamic programming we characterize the forms of both the optimal order policy for the components and the optimal assembly policy of the end product for a multiperiod problem of arbitrary but finite length we believe that this work represents the only exact analysis of an mrp type assembly system when demand is stochastic

a welfare comparison of private and public monopoly abstract the cost function of a monopoly is c q k q where is unknown to the regulator we evaluate various ownership and regulation regimes in terms of social welfare determined by both the amount of total surplus and its distribution maximal welfare is achieved by the regulated public firm when its bias is pro consumer and also when it is pro worker and is low enough we compare an unregulated public firm with a private one regulated a la loeb magat baron myerson and characterize the frontier in parameter space where one or the other dominates

inventory cost rate functions with nonlinear shortage costs this article considers five cost rate models for inventory control each summarizing the expected holding and shortage costs per period as a function of the inventory position all models have linear holding costs and shortage cost coefficients of dimension unit period unit and period the latter two coeficients may be the shadow costs of a fill rate and a ready rate service constraint respectively one of the cost rate models is a new suggestion intended to facilitate modeling of periodic review inventory systems if and only if conditions on the demand process are presented for which the cost rate is quasi convex in the inventory position the typical sufficient condition requires that the cumulative demand distribution be logconcave a condition that is met by most demand distributions commonly used in the inventory literature the results simplify optimization and extend the known optimality of s s and nq r policies to cost structures common in applications and to the presence of typical service constraints as a prerequisite for the study a series of new monotonicity results are derived for compound renewal processes

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

effective inventory control policies with a minimum order quantity and batch ordering abstract in this paper we consider a single item periodic review stochastic inventory system with both minimum order quantity moq and batch ordering requirements in each time period the firm can order either none or at least as much as the moq at the same time if an order is placed the order quantity is required to be an integral multiple of a given specific batch size we first adopt a heuristic policy which is specified by two parameters s t applying a discrete time markov chain approach we compute the system cost and optimize this s t policy under the long run average cost criterion we also consider a simpler one parameter policy the so called s policy which is a special case of the s t policy in an intensive numerical study we find that 1 both policies perform well in comparison with other policies and 2 the s policy also performs well and is compatible with the s t policy only in a few cases where demand variation is small the latter outperforms the former significantly we also evaluate the effects of some important parameters on system performance

contingent labor contracting under demand and supply uncertainty firms increasingly use contingent labor to flexibly respond to demand in many environments labor supply agencies are growing to fill this need as a result firms and agencies are engaging in long term contracts for labor supply we develop mathematical models of the interaction between firms and labor supply agencies when demand and supply are uncertain we consider two models of labor supply uncertainty termed productivity and availability uncertainty and study how each affects the nature of the contracts formed these models reflect two major roles played by the labor supply agency in the case of productivity uncertainty we find that it is possible to construct a contract that coordinates the firm and agency hiring in an optimal way in contrast we show that in environments characterized by availability uncertainty optimal contracts are not possible however there is a large range of contract parameters for which both parties would benefit from a contract we analyze these and discuss the trade offs that should be considered in contract negotiation

lower bounds for multi echelon stochastic inventory systems we establish lower bounds on the minimum cost of managing certain production distribution networks with setup costs at all stages and stochastic demands these networks include serial assembly and one warehouse multi retailer systems we obtain the bounds through novel cost allocation schemes we evaluate the bounds performance for one warehouse multi retailer systems by comparing them with simple heuristic policies the bounds are quite tight for systems with a small number of retailers we also present simplified proof of known optimality results for serial and assembly systems

source country characteristics and the inflow of foreign direct investment into saudi arabia the paper examines the impact of source country characteristics on the inflow of fdi into saudi arabia using a gravity type model including economic distance and socio political variables a unique database listing all new investments involving foreign ownership is used to construct a panel of 33 countries in the period 1980 2005 to account for many country year observations with zero fdi the negative binomial regression the tobit regression and the heckman selection procedure are used the conclusions drawn from the analysis employing panel based techniques differ from the results obtained from pooled regression models also the determinants of fdi differ depending on whether foreign investment is measured in terms of investment expenditure or the number of individual foreign projects the heckman selection results reveal that there are a large number of factors affecting the decision to invest in saudi arabia compared with relatively few determinants of the actual size of investment traditional size and distance characteristics hold to a great extent but the relationship between fdi and bilateral trade is unclear and there is some evidence that the countries that export to saudi arabia do not invest there in terms of scope for possible spillovers there is mixed evidence on whether the investment comes from more technologically advanced economies but volume wise important investments originate from countries characterised by high income per capita

coordinating investment production and subcontracting we value the option of subcontracting to improve financial performance and system coordination by analyzing a competitive stochastic investment game with recourse the manufacturer and subcontractor decide separately on their capacity investment levels then demand uncertainty is resolved and both parties have the option to subcontract when deciding on their production and sales we analyze and present outsourcing conditions for three contract types 1 price only contracts where an ex ante transfer price is set for each unit supplied by the subcontractor 2 incomplete contracts where both parties negotiate over the subcontracting transfer and 3 state dependent price only and incomplete contracts for which we show an equivalence result while subcontracting with these three contract types can coordinate production decisions in the supply system only state dependent contracts can eliminate all decentralization costs and coordinate capacity investment decisions the minimally sufficient price only contract that coordinates our supply chain specifies transfer prices for a small number 6 in our model of contingent scenarios our game theoretic model allows the analysis of the role of transfer prices and of the bargaining power of buyer and supplier we find that sometimes firms may be better off leaving some contract parameters unspecified ex ante and agreeing to negotiate ex post also a price focused strategy for managing subcontractors can backfire because a lower transfer price may decrease the manufacturer s profit finally as with financial options the option value of subcontracting increases as markets are more volatile or more negatively correlated

political manipulation of a public firm s objective function abstract in the context of a government owned public firm that competes with a private firm this paper demonstrates how the government can maximize its true objective by assigning the public firm a different objective function interestingly this assigned objective function need bear no resemblance to the actual objective being sought enabling the government to disguise a politically unpopular agenda and or outside influence

efficient supply contracts for fashion goods with forecast updating and two production modes we examine the problem of developing supply contracts that encourage proper coordination of forecast information and production decisions between a manufacturer and distributor of high fashion seasonal products operating in a two mode production environment the first production mode is relatively cheap but requires a long lead time while the second is expensive but offers quick turnaround we focus on contracts of the form w1 w2 b wherewi is the wholesale price offered for production modei andb is a return price offered for items left over at the end of the season we find that such a contract can coordinate the manufacturer and distributor to act in the best interest of the channel the pricing conditions needed to ensure an efficient solution vary depending on the degree of demand forecast improvement between periods and the manufacturer s access to forecast information we also examine whether these conditions ensure a pareto optimal solution with respect to two traditional production settings

a stock rationing policy in a s s controlled stochastic production system with 2 phase coxian processing times and lost sales abstract this paper analyzes a s s controlled stochastic production system with multi class demands and lost sales demands in each class are assumed to arrive according to a poisson process and the time required to process an item is assumed to follow a 2 phase coxian distribution for each class a stock rationing level is set when customers arrive if the inventory level is lower than the predetermined rationing level the demands are lost for future demands with higher priorities a behavior of the production system is modeled as a continuous time markov chain and an efficient algorithm to calculate the steady state probability distribution of the system is proposed the average operating cost under the stock rationing policy is compared with the one without stock rationing numerical experiment shows that the proposed stock rationing policy reduces the average operating cost significantly depending on the system parameters

real options approach based demand forecasting method for a range of products with highly volatile and correlated demand to achieve a competitive edge needed for marketing highly competitive products modern enterprises have actively sought to provide the marketplace with an expansive range of products with high random volatility of demand and correlations between demands of product consequently traditional forecasting methods for separately forecasting demand for these products are likely to yield significant deviations therefore this study develops a real options approach based forecasting model to accurately predict future demand for a given range of products with highly volatile and correlated demand additionally this study also proposes using monte carlo simulation to solve the demand forecasting model the real options approach associated with monte carlo simulation not only deals effectively with random variation involving a particular demand stochastic diffusion process but can handle the correlations in product demand

price equilibrium and willingness to pay in a vertically differentiated mixed duopoly in the framework of a vertically differentiated mixed duopoly with uncovered market and zero costs we study the existence of a price equilibrium when a welfare maximizing public firm producing low quality goods competes against a profit maximizing private firm producing high quality goods we show that a price equilibrium exists if the quality spectrum is wide enough vis a vis a measure of the convexity of the distribution of the consumers willingness to pay and that such equilibrium is unique if this sufficient condition is tightened logconcavity of the income distribution is inconsistent with the existence of equilibrium

volatility estimation for stochastic project value models one of the key parameters in modeling capital budgeting decisions for investments with embedded options is the project volatility most often however there is no market or historical data available to provide an accurate estimate for this parameter a common approach to estimating the project volatility in such instances is to use a monte carlo simulation where one or more sources of uncertainty are consolidated into a single stochastic process for the project cash flows from which the volatility parameter can be determined nonetheless the simulation estimation method originally suggested for this purpose systematically overstates the project volatility which can result in incorrect option values and non optimal investment decisions examples that illustrate this issue numerically have appeared in several recent papers along with revised estimation methods that address this problem in this article we extend that work by showing analytically the source of the overestimation bias and the adjustment necessary to remove it we then generalize this development for the cases of levered cash flows and non constant volatility in each case we use an example problem to show how a revised estimation methodology can be applied

optimal control of a divergent multi echelon inventory system consider a divergent multi echelon inventory system such as a distribution system or a production system at every facility in the system orders are placed or production is initiated periodically the order arrives after a fixed lead time at the end of each period linear costs are incurred penalty costs are incurred at the most downstream facilities for back orders the objective is to minimize the expected holding and penalty costs per period we prove that under the balance assumption it is cost optimal to control every facility by an order up to policy the optimal replenishment policy i e the order up to level and the allocation functions at each facility can be determined by system decomposition this decomposition reduces complex multi dimensional control problems to simple one dimensional problems

technical note optimal control of an assembly system with multiple stages and multiple demand classes we consider an assembly system with multiple stages multiple items and multiple customer classes the system consists of m production facilities each producing a different item items are produced in variable batch sizes one batch at a time with exponentially distributed batch production times demand from each class takes place continuously over time according to a compound poisson process at each decision epoch we must determine whether or not to produce an item and should demand from a particular class arise whether or not to satisfy it from existing inventory if any is available we formulate the problem as a markov decision process and use it to characterize the structure of the optimal policy in contrast to systems with exogenous and deterministic production lead times we show that the optimal production policy for each item is a state dependent base stock policy with the base stock level nonincreasing in the inventory level of items that are downstream and nondecreasing in the inventory level of all other items for inventory allocation we show that the optimal policy is a multilevel state dependent rationing policy with the rationing level for each demand class nonincreasing in the inventory level of all nonend items we also show how the optimal control problem can be reformulated in terms of echelon inventory and how the essential features of the optimal policy can be reinterpreted in terms of echelon inventory

capacity utilization theoretical models and empirical tests abstract this paper examines the determinants of industry capacity utilization in 40 chemical product industries over a period of roughly two decades a series of testable hypotheses are developed based on three operations research models of capacity expansion the manne model the newsboy model and the whitt luss model the hypotheses are tested on the chemical industries sample using multiple regression analysis the empirical results are consistent with most predictions derived from the newsboy and whitt luss models which suggests that firms made expansion decisions in a manner roughly in accordance with these models capacity utilization was positively related to capital intensity and the trend rate of demand growth and was negatively related to demand variability geographic plant dispersion and plant lumpiness the magnitude of investment scale economies and the extent of multi plant operation had little effect on capacity utilization

budget allocation for permanent and contingent capacity under stochastic demand we develop a model of budget allocation for permanent and contingent workforce under stochastic demand the level of permanent capacity is determined at the beginning of the horizon and is kept constant throughout whereas the number of temporary workers to be hired must be decided in each period compared to existing budgeting models this paper explicitly considers a budget constraint under the assumption of a restricted budget the objective is to minimize capacity shortages when over expenditures are allowed both budget deviations and shortage costs are to be minimized the capacity shortage cost function is assumed to be either linear or quadratic with the amount of shortage which corresponds to different market structures or different types of services we thus examine four variants of the problem that we model and solve either approximately or to optimality when possible a comprehensive experimental design is designed to analyze the behavior of our models when several levels of demand variability and parameter values are considered the parameters consist of the initial budget level the unit cost of temporary workers and the budget deviation penalty reward rates varying these parameters produce several trade offs between permanent and temporary workforce levels and between capacity shortages and budget deviations numerical results also show that the quadratic cost function leads to smooth and moderate capacity shortages over the time periods whereas all shortages are either avoided or accepted when the cost function is linear

optimizing the use of contingent labor when demand is uncertain abstract we develop a new model for flexible workforce management in environments with uncertainty in the demand for labor in particular we model a workforce comprised of regular workers who have fixed schedules and may work overtime and contingent workers whose working hours are flexible as specified by a contract over a finite planning horizon our model can represent a variety of contracts including temporary workers on call workers with guaranteed minimum pay and comp time arrangements we formulate the model as an optimization problem that determines the regular and contingent worker pool sizes that minimize expected labor and backlog costs embedded within this problem is a dynamic programming problem of making optimal operational staffing decisions with respect to the utilization of contingent and overtime resources numerical examples demonstrate the effect that the timing of information has on the benefits of flexibility we also derive structural results that may be exploited to reduce the computational effort required to use the model

approximations of dynamic multilocation production and inventory problems consider a central depot or plant which supplies several locations experiencing random demands orders are placed or production is initiated periodically by the depot the order arrives after a fixed lead time and is then allocated among the several locations the depot itself does not hold inventory the allocations are finally received at the demand points after another lag unfilled demand at each location is backordered linear costs are incurred at each location for holding inventory and for backorders also costs are assessed for orders placed by the depot the object is to minimize the expected total cost of the system over a finite number of time periods this system gives rise to a dynamic program with a state space of very large dimension we show that this model can be systematically approximated by a single location inventory problem all the qualitative and quantitative results for such problems can then be applied

option valuation of claims on real assets the case of offshore petroleum leases this paper extends financial option theory by developing a methodology for the valuation of claims on a real asset an offshore petroleum lease several theoretical and practical problems not present in applying option pricing theory to financial assets are addressed most importantly we show the necessity of combining option pricing techniques with a model of equilibrium in the market for the underlying asset petroleum reserves the advantages of this approach over conventional discounted cash flow techniques are emphasized the methodological development provides important insights for both company behavior and government policy promising empirical results are reported

integrating resource and production decisions in a simple multi stage assembly system we consider a simple multi stage assembly system with stationary stochastic demand for a single final product that is made to stock the assembly tasks are performed by human resources this workforce consists of two parts regular workforce with a long term contract and temporary workforce that are contracted based on the actual demand contracting resources early is always cheaper than contracting later when we separate resource and production decisions we can first determine order up to levels and production decisions in a standard way and afterwards find the best mix of regular and temporary workforce next to this decoupled approach we present an integrated approach where these decisions influence each other in a set of examples we show that the integrated approach can be very beneficial

the learning curve and optimal production under uncertainty this article examines the implications of the learning curve in a world of uncertainty we consider a competitive firm whose costs decline with cumulative output because the price of the firm s output evolves stochastically future production and cumulative output are unknown and are contingent on future prices and costs we derive an optimal decision rule that maximizes the firm s market value produce when the price exceeds a critical level which is a declining function of cumulative output we show how the shadow value of cumulative production the total value of the firm and the decision to produce depend on the volatility of the price and other parameters uncertainty increases the critical price required for the firm to produce but also increases the value of thefirm thus during periods of high volatility firms facing a learning curve ought to be producing less but are worth more

restricted time remembering policies for the inventory rationing problem abstract we analyse an s q inventory model with unit poisson demand several demand classes and lost sales when dealing with different demand classes the usual approach is to control the inventory by critical levels at which stock is reserved for demand of higher priority we focus on time remembering policies where the critical levels are allowed to depend on the time since the actual outstanding order if any was issued in particular we introduce a new class of policies called restricted time remembering rtr policies we divide the lead time in m intervals of time and restrict the critical levels of the rtr policy to be constant over each interval of time this policy is much easier to implement than the optimal rationing policy where the critical levels can change continuously over time and in a numerical study we show that the performance of the rtr policy is close to that of the optimal policy even when the number of intervals is 2 or 3

demand evolution in stochastic inventory systems riskiness increase abstract this paper characterizes demand evolution in the steady state under common inventory policies in a single location stochastic inventory system our results show that downstream demand nonstrictly second degree stochastically dominates upstream orders and the bullwhip effect occurs we provide the link between demand evolution and utility theory for stochastic inventory systems our model is general in that ultimate customer demand follows an arbitrary stationary distribution and the facility may arbitrarily select policy parameters

modified echelon r q policies with guaranteed performance bounds for stochastic serial inventory systems we consider the classic continuous review nstage serial inventory system with a homogeneous poisson demand arrival process at the most downstream stage stage 1 any shipment to each stage regardless of its size incurs a positive fixed setup cost and takes a positive constant lead time the optimal policy for this system under the long run average cost criterion is unknown finding a good worst case performance guarantee remains an open problem we tackle this problem by introducing a class of modified echelon r q policies that do not require qi 1 qi to be a positive integer stage i 1 ships to stage i based on its observation of the echelon inventory position at stage i if it is at or below ri and stage i 1 has positive on hand inventory then a shipment is sent to stage i to raise its echelon inventory position to ri qias close as possible we construct a heuristic policy within this class of policies which has the following features first it has provably primitive dependent performance bounds in a two stage system the performance of the heuristic policy is guaranteed to be within 1 k1 k2 times the optimal cost where k1 is the downstream fixed cost and k2 is the upstream fixed cost we also provide an alternative performance bound which depends on efficiently computable optimal r q solutions to n single stage systems but tends to be tighter second the heuristic is simple it is efficiently computable and it performs well numerically it is even likely to outperform the optimal integer ratio echelon r q policies when k1 is dominated by k2 third the heuristic is asymptotically optimal when we take some dominant relationships between the setup or holding cost primitives at an upstream stage and its immediate downstream stage to the extreme for example when h2 h1 0 where h1 is the downstream holding cost parameter and h2 is the upstream holding cost parameter

optimal policies for multi echelon inventory problems with batch ordering in many production distribution systems materials flow from one stage to another in fixed lot sizes for example a retailer orders a full truckload from a manufacturer to qualify for a quantity discount a factory has a material handling system that moves full containers of parts from one production stage to the next in this paper we derive optimal policies for multi stage serial and assembly systems where materials flow in fixed batches the optimal policies have a simple structure and their parameters can be easily determined this research extends the multi echelon inventory theory in several ways it generalizes the clark scarf model by allowing batch transfers of inventories rosling 1989 shows that assembly systems can be interpreted as serial systems under the assumption that there are no setup costs we show that the series interpretation still holds when materials flow in fixed batches which satisfy a certain regularity condition finally veinott 1965 identifies an optimal policy for a single location inventory system with batch ordering this paper generalizes his result to multi echelon settings

economic investment times for capacity expansion problems abstract a simple rule for the determination of the optimal investment time for a capacity expansion problem is provided based on a general class of stochastic demand processes of practical interest the timing rule is shown to be independent of the descriptive characteristics of the demand process and thus can be considered to be robust in nature

inventory rationing in a make to stock production system with several demand classes and lost sales this paper considers the stock rationing problem of a single item make to stock production system with several demand classes and lost sales for the case of poisson demands and exponential production times we show that the optimal policy can be characterized by a sequence of monotone stock rationing levels for each demand class there exists a stock rationing level at or below which it is optimal to start rejecting the demand of this class in anticipation of future arrival of higher priority demands a simple queueing model is analyzed to compute the operating cost of a rationing policy in a numerical study we compare the optimal rationing policy with a first come first served policy to investigate the benefit of stock rationing under different operating conditions of the system

a production inventory system with markovian capacity and outsourcing option we study the optimal production inventory outsourcing policy for a firm with markovian in house production capacity that faces independent stochastic demand and has the option to outsource we find very simple optimal policy forms under fairly reasonable assumptions in addition when the capacity markov process is stochastically monotone the policy parameters decrease in the firm s current capacity level under additional assumptions all these results extend to the infinite horizon and undiscounted cost cases we analyze comparative statics and the necessity of some technical conditions and discuss when the outsourcing option is more valuable

analysis of batch ordering inventory models with setup cost and capacity constraint abstract stochastic periodic review batch ordering inventory problems appear in many industrial settings however few literature deals with the optimal ordering polices for such problems no mention to the inclusion of the fixed ordering cost and the production capacity in this paper we consider a single item periodic review batch ordering inventory system with the consideration of the setup cost and the capacity constraint for each order over a finite planning horizon by proposing several new convex notions we show that a batch based s s policy is optimal for the unlimited ordering capacity case while for the limited ordering capacity case a modified r q policy is optimal for the setting with zero ordering setup cost and a batch based x y band policy for the setting with positive ordering setup cost moreover we analytically study the sensitivity of the policy parameters with respect to the capacity and batch order size and derive the bounds on the optimal policy parameters we further extend our analysis to the infinite horizon setting and show that the structure of the optimal policy remains similar finally the numerical experiments provide some insights into the impact of model parameters on the benefit of reducing the batch size and increasing the ordering capacity and indicate that ignoring batch requirement may lead to a significant cost increment

partial privatization in mixed duopoly abstract we investigate a quantity setting duopoly involving a private firm and a privatized firm jointly owned by the public and private sectors the private firm maximizes profits while the privatized firm takes both profits and social welfare into consideration we consider how many shares the government should hold in the privatized firm we find that neither full privatization the government does not hold any shares nor full nationalization the government holds all of the shares is optimal under moderate conditions

fighting city hall entry deterrence and technology upgrades in cable tv markets this article investigates how private firms respond to potential entry from public firms this paper uses a data set of over 3 000 u s cable tv systems to present evidence consistent with entry deterrence incumbent cable tv firms upgrade faster when located in markets with a potential municipal entrant however the same systems are then slower to offer new products enabled by the upgrade suggesting upgrades in these markets occur for strategic reasons incumbent cable systems also upgrade faster in response to municipal entry threats than to private entry threats understanding how private firms respond to potential entry from public firms is especially important in light of recent u s government entry into several industries this paper was accepted by bruno cassiman business strategy

one warehouse multiretailer systems with centralized stock information we consider a distribution system with a central warehouse and multiple retailers the warehouse orders from an outside supplier and replenishes the retailers which in turn satisfy customer demand the retailers are nonidentical and their demand processes are independent compound poisson there are economies of scale in inventory replenishment which is controlled by an echelon stock batch transfer policy for the special case with simple poisson demand we develop an exact method for computing the long run average holding and backorder costs of the system based on this exact method we provide approximations for compound poisson demand numerical examples are used to illustrate the accuracy of the approximations we also present a numerical comparison between the average costs of a heuristic echelon stock policy and an existing lower bound on the average costs of all feasible policies

coordination mechanisms in decentralized serial inventory systems with batch ordering this paper studies a periodic review serial supply chain in which materials are ordered and shipped according to r nq policies three information scenarios are considered depending on the level of information available echelon local and quasilocal in the echelon scenario each stage can access the inventory and cost information within its echelon comprising the stage itself and all downstream stages in the local scenario each stage only accesses its own local information finally in the quasilocal scenario each stage knows its local information plus the actual customer demands we propose coordination schemes that regulate the stages to achieve the supply chain s optimal cost under each information setting all these coordination schemes fit comfortably within an emerging practice called supply chain finance which includes the organization and technology needed to implement them

impact of sourcing flexibility on the outsourcing of services under demand uncertainty abstract this paper investigates the relationship between market conditions and the value and use of sourcing flexibility for service processes we develop and analyze a series of models and we derive expressions for the optimal switching decision the value of the option to outsource the value of the option to backsource and the probability and timing of switches between the alternative sources one contribution is the models and associated derivations which are largely new to the literature and may serve as a tool to support service sourcing plans and decisions the second contribution is a series of results with managerial implications 1 the probability of outsourcing is generally increasing in volatility for high skill process and decreasing in volatility for low skill processes earlier work has found that the hysteresis band is increasing in volatility which is interpreted as an indicator of increasing organizational inertia we also find that the hysteresis band is increasing in volatility but interestingly for the case of high skill processes organizational inertia tends to be decreasing in volatility 2 the option to backsource is generally more valuable for high skill processes than for low skill processes this result suggests that investments to make it easier to backsource should have a higher priority for high skill processes 3 the value of the option to backsource a high skill service process can be decreasing in volatility the result suggests that a rather nuanced consideration of volatility is in order when considering investments in the flexibility to backsource a high skill process

mixed oligopoly equilibria when firms objectives are endogenous abstract we study a vertically differentiated market where two firms simultaneously choose the quality and price of the good they sell and where consumers may also care for the average quality of the goods supplied firms are composed of two factions whose objectives differ one is maximizing profit while the other maximizes revenues the equilibrium concept we model called firm unanimity nash equilibrium fune corresponds to the nash equilibrium between firms when there is efficient bargaining between the two factions inside both firms we first show that such equilibria are inefficient with both firms underproviding quality we then assume that the government takes a participation in one firm which introduces a third faction bent on welfare maximization in that firm we study the characteristics of equilibria as a function of the bargaining weight of the welfare maximizing faction we show that equilibrium welfare increases with this bargaining weight especially if consumers care a lot for the average quality of the goods provided

capacity investment timing by start ups and established firms in new markets we analyze the competitive capacity investment timing decisions of both established firms and start ups entering new markets which have a high degree of demand uncertainty firms may invest in capacity early when uncertainty is high or late when uncertainty has been resolved possibly at different costs established firms choose an investment timing and capacity level to maximize expected profits whereas start ups make those choices to maximize the probability of survival when a start up competes against an established firm we find that when demand uncertainty is high and costs do not decline too severely over time the start up takes a leadership role and invests first in capacity whereas the established firm follows by contrast when two established firms compete in an otherwise identical game both firms invest late we conclude that the threat of firm failure significantly impacts the dynamics of competition involving start ups this paper was accepted by yossi aviv operations management

coordinating inventory control and pricing strategies under batch ordering in this paper we investigate joint pricing and inventory control problems in a finite horizon single product periodic review setting with certain uncertain supply capacities the demands in different periods are random variables whose distributions depend on the posted price exhibiting the additive form the order quantity in each period is required to be of integral multiples of a given specific batch size denoted by q inventory replenishment incurs a linear ordering cost referred to as the cost rate function the sum of holding and backorder costs can either be convex or quasi convex the objective is to determine a joint ordering and pricing decision that can maximize the total expected profit over the planning horizon we first consider the case in which the cost rate function is convex and show that the modifiedr q list price policy is optimal for the system with certain and limited capacities a special case of which is the r q list price policy when capacities become unlimited as supply capacities become random the optimal policy follows a new structure wherein the optimal order up to level and posted price must be coordinated to make the optimal safety stock level follow the r q policy we further consider the case of a quasi convex cost rate function which may arise when a service level constraint is used as a surrogate for the shortage cost we demonstrate that the r q list price policy is optimal for the system without supply capacity constraints in addition extensions to several other models are discussed the enabling technique is based on the notion of q jump convexity and its variants

technical note on optimal policies for inventory systems with batch ordering we study a periodically reviewed multiechelon inventory system in series such that order quantities at every stage have to be multiples of a given stage specific batch size the batch sizes are nested in the sense that the batch size for every stage is an integer multiple of the batch size for its downstream stage the problem is that of determining the policy that minimizes the expected discounted sum of costs over a finite horizon the result is that an echelon r nq policy is optimal when demands are independent across periods or more generally markov modulated we also comment on algorithmic implications of our result and on extensions

machine and labor flexibility in manufacturing networks abstract many industrial companies today operate under strict employment legislation and work agreements since flexible capacity has been widely recognized as an important hedge against uncertain demand there exist strong efforts to introduce more flexible workforce models in this paper we investigate the benefits of such labor flexibility and its interplay with machine flexibility from a network capacity investment perspective we consider a firm that has to invest simultaneously in labor and machine capacity under uncertain demand and a given network configuration while anticipating the deployment of labor flexibility after demand has been realized instruments of labor flexibility range from temporary employment to personnel transfers between plants the underlying decision problem is formulated as a two stage stochastic program with recourse based on numerical studies and the analysis of a stylized model we demonstrate the impact of labor flexibility on the optimal levels of machine and labor capacity we compare the benefits obtained by personnel transfers with those of temporary workers and find that temporary employment always decreases the number of permanent workers while personnel transfers may even allow for a larger workforce our results further indicate that personnel transfers are more effective in larger manufacturing networks although these benefits are decreasing when most plants in the network are capable of producing more than one product machine flexibility finally we present evidence for the efficiency of a combined usage of personnel transfers and temporary workers

dynamic inventory rationing strategies for inventory systems with two demand classes poisson demand and backordering we study inventory systems with two demand classes critical and non critical poisson demand and backordering we analyze dynamic rationing strategies where the number of items reserved for critical demand depends on the remaining time until the next order arrives different from results in the literature we do not discretize demand but derive a set of formulae that determine the optimal rationing level for any possible value of the remaining time moreover we show that the cost parameters can be captured in a single relevant dimension which allows us to present the optimal rationing levels in charts and lookup tables that are easy to implement numerical examples illustrate that the optimal dynamic rationing strategy outperforms all static strategies with fixed rationing levels

duopoly and quality standards abstract in the absence of sunk costs a low quality producer benefits from a mildly restrictive quality standard whereas a high quality producer suffers from it consumers welfare increases if the firm producing the higher quality does not increase its quality significantly in response to the increase in quality by its rival a sufficiently severe standard causes exit from the industry when there are no sunk cost the high quality producer exits first