optimal dynamic pricing of inventories with stochastic demand over finite horizons in many industries managers face the problem of selling a given stock of items by a deadline we investigate the problem of dynamically pricing such inventories when demand is price sensitive and stochastic and the firm s objective is to maximize expected revenues examples that fit this framework include retailers selling fashion and seasonal goods and the travel and leisure industry which markets space such as seats on airline flights cabins on vacation cruises and rooms in hotels that become worthless if not sold by a specific time we formulate this problem using intensity control and obtain structural monotonicity results for the optimal intensity resp price as a function of the stock level and the length of the horizon for a particular exponential family of demand functions we find the optimal pricing policy in closed form for general demand functions we find an upper bound on the expected revenue based on analyzing the deterministic version of the problem and use this bound to prove that simple fixed price policies are asymptotically optimal as the volume of expected sales tends to infinity finally we extend our results to the case where demand is compound poisson only a finite number of prices is allowed the demand rate is time varying holding costs are incurred and cash flows are discounted the initial stock is a decision variable and reordering overbooking and random cancellations are allowed

on the structure of lost sales inventory models we provide a new approach to the structural analysis of the standard lost sales inventory system this approach is we think easier to work with than the original one we also derive new bounds on the optimal policy then we show that more variable demand leads to higher cost finally we extend the analysis to several important variations of the basic model

accounting rates of return many economic studies provide empirical evidence regarding cross sectional differences in firm profitability in most of these studies firm profitability is measured by an accounting rate of return net income dividend by the book value of assets hereafter arr rather than an economic rate of profit franklin fisher and john mcgowan define the firm s economic rate of profit irr as that interest rate which equates the present value of its net revenue stream to its initial outlay 1983 p 82 fisher and mcgowan examine the analytic relation between a firm s arr and its irr in a series of examples and conclude that the arr is such a bad surrogate for the irr that the results of arr based empirical studies are likely to be totally misleading p 91 william long and david ravenscraft 1984 have criticized the theoretical work of fisher and mcgowan because the nature of the analytic relationship between the arr and the irr in the context of highly simplified hypothetical examples may not be indicative of the nature of the relationship in empirical settings their criticism adopts the utilitarian view that the arr has to be treated as a suitable surrogate for the irr as long as no preferable alternative measure of profitability is available for empirical work this view has merit as long as the measurement error which is contained in the arr is random rather than systematic unfortunately the nature and extent of the measurement error which is contained in the arr in a particular empirical setting can only be determined unequivocally if the irr is unequivocally known in such a case of course there would be no need to rely on the arr at all due to this unhappy circle empirical research on firm profitability has continued to rely on the arr despite the fact that many persons reasonably believe that the results of such research may be totally misleading fisher and mcgowan g c harcourt 1965 while others reasonably believe that the results are reliable enough to form a basis for policy decisions long and ravenscraft recent work by y ijiri 1978 1979 1980 and by myself 1982 has shown that conditional irr estimates can be obtained from data in firms financial statements while these irr estimates are conditional they do abstract from certain extraneous factors that influence arrs and that differ across firms consequently the conditional irr estimates are free from some of the sources of measurement error which are known to contaminate the arr thus the conditional irr estimates can be used to provide evidence on whether these sources of measurement error have or have not affected the outcome of prior studies in which profitability was measured by the arr such evidence can help to objectively resolve the conflict between the opposing views on the reliability of arr based profitability research this paper uses conditional irr estimates to examine the properties of the measurement error in the arr in a study of the relationship between firm profitability and firm size the remainder of the paper is organized as follows in section i the theoretical work of fisher and mcgowan is used professor of accounting university of iowa iowa city ia 52242 i gratefully acknowledge the comments of william albrecht dan dhaliwal gary fethke franklin fisher scott linn william r kinney jr and the participants of a workshop at the university of florida on earlier versions of this paper 1 some authors for example william long and david ravenscraft 1984 have used the sales margin ratio earnings sales as a measure of profitability however if one views profitability as return per unit of sacrifice the sales margin ratio is not a profitability measure since it ignores the sacrifice or investment required to generate a dollar of sales consequently this paper does not attempt to shed any insight into prior studies that have relied on the sales margin ratio as a measure of profitability

the energy efficiency paradox revisited through a partial observability approach the present paper examines the energy efficiency paradox demonstrated in greek manufacturing firms through a partial observability approach the data set used has resulted from a survey carried out among 161 energy saving technology firm adopters maximum likelihood estimates that arise from an incidental truncation model reveal that the adoption of the energy saving technologies is indeed strongly correlated to the returns of assets that are required in order to undertake the corresponding investments the source of the energy efficiency paradox lies within a wide range of factors policy schemes that aim to increase the adoption rate of energy saving technologies within the field of manufacturing are significantly affected by differences in the size of firms finally mixed policies seem to be more effective than policies that are only capital subsidy or regulation oriented

integrating replenishment decisions with advance demand information there is a growing consensus that a portfolio of customers with different demand lead times can lead to higher more regular revenues and better capacity utilization customers with positive demand lead times place orders in advance of their needs resulting inadvance demand information this gives rise to the problem of finding effective inventory control policies under advance demand information we show that state dependent s s and base stock policies are optimal for stochastic inventory systems with and without fixed costs the state of the system reflects our knowledge of advance demand information we also determine conditions under which advance demand information has no operational value a numerical study allows us to obtain additional insights and to evaluate strategies to induce advance demand information

optimal dynamic scheduling policy for a make to stock production system this paper considers the dynamic scheduling problem of a single server make to stock queue with two products for the case of poisson demands and exponential production times we show that it is optimal to produce the product with the larger b index when it is backordered if the production times are identically distributed the optimal policy can further be characterized by monotone switching curves we also prove that a base stock policy coupled with a switching curve is optimal for some initial inventory levels a simple linear switching rule for determining production priority is proposed and compared with other heuristic policies in a computational experiment

stock rationing under service level constraints in a vertically integrated distribution system this paper addresses a rationing problem in a two level vertically integrated distribution system composed of one manufacturer and several retail points the motivating case developed in the vending machine sector and modeled as a newsvendor like problem is representative of many real settings where short term changes in demand can be substantial while capacity modification is not a viable option the paper provides an analytical discussion of the problem from two different standpoints a pure profit maximization perspective and a minimum service level perspective both subject to a product availability constraint that affects the service level the company can provide and the related expected profit by analyzing the lagrangean formulation of the problem we devise efficient computational procedures based on dichotomy search to find the optimal allotments to retailers maximizing the expected profit and ensuring a minimum service level then we extend the analysis to the evaluation of the highest service level that can be provided under a product availability constraint we identify conditions such that the proposed search procedures succeed in finding the optimal solutions as well as bounds for the search domains the proposed approach is legitimated under several demand distribution functions subject to a few commonly adopted restrictions that encompass many of the usually adopted continuous distributions finally the paper presents a three step decision making framework using the proposed procedures summarizing the decision paths the manufacturer might follow in order to optimize the allocation decision

the economic effect of immigration policies analyzing and simulating the u s case abstract in this paper we analyze the economic effects of different immigration policies using a model that incorporates economic and policy features crucial to understanding the migrant flows into the us we differentiate among the most relevant channels of immigration to the us family based employment based and undocumented moreover we explicitly account for earning incentives to migrate and for the role of immigrant networks in generating immigration opportunities hence we can analyze the effect of policy changes through those channels in our simulations comparing long run steady states highly skilled employment and unskilled immigrants generate larger surplus to us firms than natives do hence policies restricting their entry either directly or indirectly have a depressing effect on job creation and in turn on native labor markets our analysis gives new insights into the effect of policies as it accounts for the endogenous immigration response which is overlooked by most existing models

dynamic capacity management with substitution we examine a multiperiod capacity allocation model with upgrading there are multiple product types corresponding to multiple classes of demand and the firm purchases capacity of each product before the first period within each period after demand arrives products are allocated to customers customers who arrive to find that their product has been depleted can be upgraded by at most one level we show that the optimal allocation policy is a simple two step algorithm first use any available capacity to satisfy same class demand and then upgrade customers until capacity reaches a protection limit so that in the second step the higher level capacity is rationed we show that these results hold both when all capacity is salvaged at the end of the last demand period as well as when capacity can be replenished in the latter case an order up to policy is optimal for replenishment although finding the optimal protection limits is computationally intensive we describe bounds for the optimal protection limits that take little effort to compute and can be used to effectively solve large problems using these heuristics we examine numerically the relative value of strictly optimal capacity and dynamic rationing the value of perfect demand information and the impact of demand and economic parameters on the value of optimal substitution

the economic consequences of accounting choice implications of costly contracting and monitoring abstract in this paper we review research into the economic consequences of voluntary and mandatory choices of accounting techniques and standards we discuss how the predictions of extant economic consequence theories are driven by contracting and monitoring costs associated with management compensation contracts bond covenants regulation and or political visibility we review empirical tests of economic consequence theories categorize those tests and discuss their strengths and weaknesses the empirical tests reveal two systematic associations with accounting choice size a proxy for political visibility and leverage a proxy for contracting and monitoring costs of lending agreements interpretation of the results is difficult due to general limitations of the tests we conclude by suggesting some directions for future research based on our analysis of the potential payoffs associated with different types of empirical tests

a dynamic rationing policy for continuous review inventory systems stock rationing is an inventory policy that allows differential treatment of customer classes without using separate inventories in this paper we propose a dynamic rationing policy for continuous review inventory systems which utilizes the information on the status of the outstanding replenishment orders for both backordering and lost sales environments we conduct simulation studies to compare the performance of the dynamic policy with the static critical level and the common stock policies and quantify the gain obtained we propose two new bounds on the optimum dynamic rationing policy that enables us to tell how much of the potential gain the proposed dynamic policy realizes we discuss the conditions under which stock rationing both dynamic and static is beneficial and assess the value of the dynamic policy

effects of enforcement on illegal markets evidence from migrant smuggling along the southwestern border abstract the paper analyzes the effects of tighter border control on the illegal crossing market between mexico and the united states combining panel data on illegal migrants with enforcement statistics the effects of enforcement are found to be moderate prices of border smugglers coyotes increased by only 17 while the demand for smugglers has remained unchanged enforcement has however shifted illegal migrants to remote crossing places border crossing is now more time intensive with higher prices for coyotes and risk of death this geographic substitution raised migration costs by 140 more than twice the effect of enforcement on smuggling prices

a make to stock system with multiple customer classes and batch ordering this paper examines the impact of customer order sizes on a make to stock system with multiple demand classes we first characterize the manufacturer s optimal production and rationing policies when the demand is nonunitary and lost if unsatisfied we also investigate the optimal policies of a backorder system with two demand classes and fixed order sizes through a numerical study we show the effects of batch orders on the manufacturer s inventory cost as well as on the benefit of optimal stock rationing it is shown that batch ordering may reduce the manufacturer s overall cost if carefully introduced in a first come first served fcfs system with the same effective demand rates the customers order sizes also have a strong impact on the benefit of optimal stock rationing

centralized admission and production control in a two stage supply chain with single component and customized products abstract this paper considers a two stage supply chain that a make to stock facility produces a single component in anticipation of future demand and a make to order facility produces customized products using components with the option of to accept or reject each customer order we address the problem of centralizing the admission and production control that maximizes the supply chain s profit subject to the system costs using a markov decision process model we characterize the structure of the optimal admission control and production policy and establish the monotonic impact of system parameters on the optimal policy two heuristics are presented and their performance is numerically compared to the optimal policy under different operating conditions of the system

mexico u s immigration effects of wages and border enforcement in this article i study how relative wages and border enforcement affect immigration from mexico to the u s to do this i develop a discrete choice dynamic programming model where people choose from a set of locations in both the u s and mexico while accounting for the location of one s spouse when making decisions i estimate the model using data on individual immigration decisions from the mexican migration project counterfactuals show that a 10 increase in mexican wages reduces migration rates and durations overall decreasing the number of years spent in the u s by about 5 a 50 increase in enforcement reduces migration rates and increases durations of stay in the u s and the overall effect is a 7 decrease in the number of years spent in the u s

dynamic pricing through discounts for optimizing multiple class demand fulfillment in a multiple customer class model of demand fulfillment for a single item we consider the use of dynamic price discounts to encourage backlogging of demand for customer classes denied immediate service customers are assumed to arrive over several stages in a period and customer classes are distinguished by their contractual price and sensitivity to discounts through dynamic programming we determine the optimal discounts to offer assuming a linear model for the sensitivity of customers to such inducements we show that customers are served in class order and allocation of inventory to demand is determined by considering the current number of customers backlogged as well as the current inventory position through comparison to a naive supplier allocating inventory first come first served with no discounting we show that profits are primarily influenced by the allocation of capacity and the use of price discounts primarily benefits the second class customers overall fill rate heuristics for implementation of the solution in real time settings are given

illegal immigration border enforcement and relative wages evidence from apprehensions at the u s mexico border we examine illegal immigration in the united states from mexico over the period 1976 1995 one challenge is that we do not observe the number of individuals that attempt to enter the united states illegally we only observe the number of individuals apprehended attempting to cross the u s mexico border illegally based on a simple migration model we postulate the existence of an apprehensions function which expresses apprehensions at the border as a function of illegal attempts to cross the border and u s border enforcement effort we find that a 10 decrease in the mexican real wage leads to a 7 5 to 8 8 increase in apprehensions at the border excerpt

managing an assemble to order system with after sales market for components abstract in this paper we consider an assemble to order manufacturing system producing a single end product assembled from n components and serving an after sales market for individual components components are produced in a make to stock fashion one unit at a time on independent production facilities production times are exponentially distributed with finite production rates the components are stocked ahead of demand and therefore incur a holding cost rate per unit demand for the end product as well as for the individual components occurs continuously over time according to independent poisson streams in order to characterize the optimal production and inventory rationing policies we formulate such a problem using a markov decision process framework in particular we show that the optimal component production policy is a state dependent base stock policy we also show that the optimal component inventory rationing policy is a rationing policy with state dependent rationing levels recognizing that such a policy is generally not only difficult to obtain numerically but also is difficult to implement in practice we propose three heuristic policies that are easier to implement in practice we show that two of these heuristics are highly efficient compared to the optimal policy in particular we show that one of the two heuristics strikes a balance between high efficiency and computational effort and thus can be used as an effective substitute of the optimal policy

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

admission and inventory control of a single component make to order production system with replenishment setup cost and lead time abstract we consider the admission control and inventory management problems of a single component make to order production system components are purchased from suppliers in batches of fixed size subject to stochastic lead times and setup costs a control policy specifies when a batch of components is purchased and whether the demand for each mto production is accepted upon arrival we formulate the problem as a markov decision process mdp model and characterize the structure of optimal admission control and inventory replenishment policies we show that a state dependent base stock policy is optimal for the inventory replenishment although the mdp value function is not necessarily convex we also show that the optimal admission control can be identified as a lattice dependent policy a sensitivity analysis is conducted to show how the optimal policy changes as a function of the system parameters to effectively coordinate admission and inventory control decisions we propose simple implementable and yet effective heuristic policies our extensive numerical results suggest that the proposed heuristics can greatly help firms to effectively coordinate their admission and inventory control activities

revenue management approach to stochastic capacity allocation problem abstract to formulate stochastic capacity allocation problems in a manufacturing system the concept and techniques of revenue management is applied in this research it is assumed the production capacity is stochastic and hence its exact size cannot be forecasted in advance at the time of planning there are two classes of frequent and occasional customers demanding this capacity the price rate as well as the penalty for order cancellation caused by overbooking is different for each class the model is developed mathematically and we propose an analytical solution method the properties of the optimal solution as well as the behavior of objective function are also analyzed the objective function is not concave in general however we prove it is a unimodal function and by taking advantage of this property the optimal solution is determined

reduce shortage with self reservation policy for a manufacturer paying both fixed and variable stockout expenditure this study considers a single item make to stock system with continuous time production and inventory controls to meet bulk demand with an exponential inter arrival time a key issue in this system is the non convex shortage cost consisting of fixed and variable expenditures when the demand is not fully satisfied we propose a self reservation policy by building a markov decision process to minimize the overall cost we find that the optimal production control is still a base stock policy but the structure of the optimal self reservation policy is very complicated however if the effective outstanding variable shortage cost is sufficiently large the optimal self reservation policy has an easy form of reserve all or nothing our numerical examples indicate the optimal policy may reduce the total average cost by 47 on average

multi class dynamic inventory rationing with stochastic demands and backordering dynamic inventory rationing is considered for systems with multiple demand classes stationary stochastic demands and backordering in the literature dynamic programming has been often applied to address this type of problems however due to the curse of dimensionality computation is a critical challenge for dynamic programming in this paper an innovative two step approach is proposed based on an idea similar to the certainty equivalence principle first the deterministic inventory rationing problem is studied where the future demands are set to be the expectation of the stochastic demand processes the important properties obtained from solving the problem with the kkt conditions are then used to develop effective dynamic rationing policies for stochastic demands which gives closed form expressions for dynamic rationing thresholds these expressions are easy to calculate and are applicable to any number of demand classes numerical results show that the expressions are close to and provide a lower bound for the optimal dynamic thresholds they also shed light on important managerial insights for example the relation between different parameters and the rationing thresholds

capacity rationing decision procedures with order profit as a continuous random variable abstract when expected demand is more than available capacity a make to order manufacturer should take the more profitable orders and reject the less profitable orders in order to better allocate its limited capacity and maximize its profit however various orders will arrive at different times in the future so the manufacturer cannot look at all the order inquiries at the same time and choose the most profitable ones when an order inquiry arrives the manufacturer must promptly determine without knowing exactly what the future orders might be whether to accept the order or to reject the order thus reserving the capacity for future more profitable orders this study focuses on such an order selection decision problem under the following assumptions 1 the arrival of future customer orders is a poisson process 2 the capacity requirement of a future customer order is a continuous random variable and 3 the profit per unit capacity used by an order is also a continuous random variable under the stochastic problem assumptions this study investigates two decision procedures that determine whether to accept or to reject an order inquiry based on the available information including 1 current available manufacturing capacity 2 capacity requirement by the order and 3 the profit per unit capacity of the order one procedure is called static probability capacity rationing decision procedure spcr the other one is called dynamic stochastic capacity rationing decision procedure dscr simulation experiments are conducted to validate the proposed procedures an optimal solution method that uses 0 1 knapsack problem formulation to obtain the decisions with perfect information is used to measure the effectiveness of the proposed procedures the results show that the approach utilizing dscr outperforms other approaches by providing the highest profit and is also very robust under various problem conditions

international migration self selection and the distribution of wages evidence from mexico and the united states we use the 1990 and 2000 mexican and u s population censuses to test borjas s negative selection hypothesis that the less skilled are those most likely to migrate from countries with high skill premia earnings inequality to countries with low skill premia earnings inequality we find that mexican immigrants in the united states are more educated than nonmigrants in mexico and were mexican immigrants to be paid according to current skill prices in mexico they would be concentrated in the middle of mexico s wage distribution these results are inconsistent with the negative selection hypothesis and instead suggest that there is intermediate selection of immigrants from mexico

design and evaluation of a dynamic capacity apportionment procedure abstract deploying a decision theory based approach we develop a heuristic for short term constrained capacity allocation to multiple product classes in make to order manufacturing attempting to maximize profit by discriminating between product classes efficacy of the heuristic is evaluated by comparing its performance to a base case and an upper bound under a wide variety of operational conditions such as variations in profit attractiveness capacity tightness customer order size structure customer order rate structure and demand coefficient of variation considering three different scenarios of time variant order rate of products the results indicate that the heuristic is effective in obtaining increased profit when capacity is very tight and products are well differentiated on average it yields an increase of 9 38 in total profit with a concomitant decrease of 0 85 in capacity utilization the results of this study serve to highlight the value of proactively seeking to differentiate products particularly when demand exceeds capacity

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

optimal policies for inventory systems with priority demand classes we consider a periodic review inventory system with two priority demand classes one deterministic and the other stochastic the deterministic demand must be met immediately in each period however the units of stochastic demand that are not satisfied during the period when demand occurs are treated as lost sales at each decision epoch one has to decide not only whether an order should be placed and how much to order but also how much demand to fill from the stochastic source the firm has the option to ration inventory to the stochastic source i e not satisfy all customer demand even though there is inventory in the system we first characterize the structure of the optimal policy we show that in general the optimal order quantity and rationing policy are state dependent and do not have a simple structure we then propose a simple policy called s k s policy wheres ands ordering policy determine when and how much to order whilek rationing policy specifies how much of the stochastic demand to satisfy we report the results of a numerical study which shows that this simple policy works extremely well and is very easy to compute

the stochastic dynamic production inventory lot sizing problem with service level constraints abstract this paper addresses the multi period single item inventory lot sizing problem with stochastic demands under the static dynamic uncertainty strategy of bookbinder and tan manage sci 34 1988 1096 in the static dynamic uncertainty strategy the replenishment periods are fixed at the beginning of the planning horizon but the actual orders are determined only at those replenishment periods and will depend upon the demand that is realised their solution heuristic was a two stage process of firstly fixing the replenishment periods and then secondly determining what adjustments should be made to the planned orders as demand was realised we present a mixed integer programming formulation that determines both in a single step giving the optimal solution for the static dynamic uncertainty strategy the total expected inventory holding ordering and direct item costs during the planning horizon are minimised under the constraint that the probability that the closing inventory in each time period will not be negative is set to at least a certain value this formulation includes the effect of a unit variable purchase production cost which was excluded by the two stage bookbinder tan heuristic an evaluation of the accuracy of the heuristic against the optimal solution for the case of a zero unit purchase production cost is made for a wide variety of demand patterns coefficients of demand variability and relative holding cost to ordering cost ratios the practical constraint of non negative orders and the existence of the unit variable cost mean that the replenishment cycles cannot be treated independently and so the problem cannot be solved as a stochastic form of the wagner whitin problem applying the shortest route algorithm

mobility and the return to education testing a roy model with multiple markets self selected migration presents one potential explanation for why observed returns to a college education in local labor markets vary widely even though u s workers are highly mobile to assess the impact of self selection on estimated returns this paper first develops a roy model of mobility and earnings where workers choose in which of the 50 states plus the district of columbia to live and work available estimation methods are either infeasible for a selection model with so many alternatives or place potentially severe restrictions on earnings and the selection process this paper develops an alternative econometric methodology that combines lee s 1983 parametric maximum order statistic approach to reduce the dimensionality of the error terms with more recent work on semiparametric estimation of selection models e g ahn and powell 1993 the resulting semiparametric correction is easy to implement and can be adapted to a variety of other polychotomous choice problems the empirical work which uses 1990 u s census data confirms the role of comparative advantage in mobility decisions the results suggest that self selection of higher educated individuals to states with higher returns to education generally leads to upward biases in ols estimates of the returns to education in state specific labor markets while the estimated returns to a college education are significantly biased correcting for the bias does not narrow the range of returns across states consistent with the finding that the corrected return to a college education differs across the u s the relative state to state migration flows of college versus high school educated individuals respond strongly to differences in the return to education and amenities across states

the role of inventory in delivery time competition the paper operationalizes the notion of shortage cost by considering the behavior of customers and competing firms and examines the role of inventory in response time competition we start with a single firm production control model in which customers are characterized by their preferences of price quality and delivery time the optimal production inventory policy and the optimal choice between make to order and make to stock operations are determined in simple newsboy like formulas the basic model is then extended to an n firm market game in which firms compete for orders from the aspect of early delivery one could think of this setting as an oligopoly racing market the analysis shows that competition can breed a demand for produce to stock just as other economic phenomena such as economies of scale uncertainty or seasonality can induce make to stock and that delivery time competition increases the buyer s welfare while decreasing the producer s welfare

the effect of commonality on safety stock in a simple inventory model we examine the effects of component commonality on optimal safety stock levels in a two product two level inventory model the criterion is to minimize system safety stock subject to a service level constraint although our model is specialized its analysis provides insights not available in other multilevel inventory models

component rationing for available to promise scheduling in configure to order systems abstract we address the problem of rationing common components among multiple products in a configure to order system with order configuration uncertainty the objective of this problem is to maximize expected revenue by implementing a threshold rationing policy under this policy a product is available to promise if fulfilling the order for the product will not cause the inventory of any one of its required components to fall below the component s threshold level for that product the problem is modeled as a two stage stochastic integer program and solved using the sample average approximation approach a heuristic is developed to generate good feasible solutions and lower bound estimates using industry data we examine the benefit of component rationing as compared to a first come first served policy and show that this benefit is correlated to the average revenue per product and the variability in the revenue across products whose components are constrained

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

capacity management for contract manufacturing contract manufacturers sell capacity under different terms to different buyers in a common practice the supplier offers a market standard price and lead time combination for products listed in its catalog at the same time it strikes contracts with some high volume customers who require recurring delivery of a custom product at a short notice usually timed to meet the buyer s production schedule whereas the manufacturer is obligated to satisfy demand from these customers it can dynamically choose which transactional orders to accept in this paper we analyze two scenarios in the first scenario the manufacturer produces contractual orders on a make to order basis and in the second it maintains finished goods inventory for such orders at each decision epoch the manufacturer decides which transactional orders to accept to maximize its long run expected profit when contractual items are made to stock the manufacturer also chooses how much extra capacity to allocate to contractual items over and above what is needed to meet realized demand we establish the structure of the optimal policies and propose scalable heuristics when optimal policies are hard to compute implement our models are then used to study the effect of demand variability on the optimal profit we also show how the amount of capacity available relative to demand changes the desirability of serving either transactional only or both markets

self selection and the earnings of immigrants this paper analyzes the way in which the earnings of the immigrant population may be expected to differ from the earnings of the native population because of the endogeneity of the decision to migrate the empirical study shows that differences in the u s earnings of immigrants with the same measured skills but from different home countries are attributable to variations in political and economic conditions in the countries of origin at the time of migration excerpt

the economics of temporary migrations many migrations are temporary a fact that has often been ignored in the economic literature on migration such omission may be serious in that expected migration temporariness can impart a distinct dynamic element to immigrants economic behavior generating possible consequences for nonmigrants in both home and host countries in this paper we provide a thorough examination of the various aspects of temporary migrations that matter for the analysis of economic phenomena we demonstrate the extent of temporary migrations in population movements we show how temporariness can affect the various economic choices and how better data have improved both the measurement of nonpermanent migrations and the analyses of various aspects of migrant behavior we propose a general theoretical framework for modeling temporary migration decisions based on which we outline the various motives for temporariness while simultaneously reviewing related literature and available data sources we discuss the possible consequences of migration temporariness for nonmigrants in both home and host countries jel f22 f24 j11 j61 k37 o15

immigration wages and education a labour market equilibrium structural model recent literature analysing wage effects of immigration assumes labour supply is fixed across education experience cells this article departs from this assumption estimating a labour market equilibrium dynamic discrete choice model on u s micro data for 1967 2007 individuals adjust to immigration by changing education participation and or occupation adjustments are heterogeneous 4 2 26 2 of prime aged native males change their careers of them some switch to white collar careers and increase education by about three years others reduce labour market attachment and reduce education also by about three years these adjustments mitigate initial effects on wages and inequality natives that are more similar to immigrants are the most affected on impact but also have a larger margin to adjust and differentiate adjustments also produce a self selection bias in the estimation of wage effects at the lower tail of the distribution which the model corrects

a single product inventory model for multiple demand classes we consider a single product inventory system that serves multiple demand classes which differ in their shortage costs or service level requirements we assume a critical level control policy and a backorder clearing mechanism in which we treat a backorder for a lower priority class equivalent to a reserve stock shortfall for the higher priority class we show the equivalence between this inventory system and a serial inventory system based on this equivalence we develop a model for cost evaluation and optimization under the assumptions of poisson demand deterministic replenishment lead time and a continuous review q r policy with rationing we propose a computationally efficient heuristic and develop a bound on its performance we provide a numerical experiment to show the effectiveness of the heuristic and the value from a rationing policy finally we describe how to extend the model to permit service times and how to extend the model to a multi echelon setting

value of capacity pooling in supply chains with heterogeneous customers we investigate the value of pooling capacity in supply chains that serve product demands of different variabilities we build and analyze models that integrate production queuing models with base stock inventory systems serving demands with different inter arrival time distributions the first model combines hyperexponential and exponential demand inter arrival time distributions exact analysis of the model allows us to develop insights into the impact of the difference in demand variabilities on the value of pooling capacity simulation experiments allow us to validate these insights for more general settings we then find one special case that combines exponential and deterministic demand arrivals with deterministic service where pooling capacity results in increasing the total cost

coming out of the shadows learning about legal status and wages from the legalized population the 1986 immigration reform and control act irca granted amnesty to approximately 1 7 million long term unauthorized workers in an effort to bring them out of the shadows and improve their labor market opportunities an analysis of wages using panel data for a sample of legalized men provides evidence that wage determinants are structurally different after amnesty for them but not for the comparison group as measured during the same time periods the wage penalty for being unauthorized is estimated to range from 14 to 24 the wage benefit of legalization under irca was approximately 6

what s driving mexico u s migration a theoretical empirical and policy analysis using data gathered in 25 mexican communities the authors link individual acts of migration to 41 theoretically defined individual household community and macroeconomic level predictors the indicators vary through time to yield a discrete time event history analysis over the past 25 years probabilities of first repeat and return migration have been linked more to the forces identified by social capital theory and the new economics of migration than to the cost benefit calculations assumed by the neoclassical model the authors find that mexico u s migration stems from three mutually reinforcing processes social capital formation human capital formation and market consolidation

market structure and market value while the use of market models to determine the sources of economic profits is quite new at least two empirical studies considering the market structure and market value relation have appeared to date interestingly they conflict thomadakis 1977 found a close positive relation between the four firm concentration ratio and relative excess valuation measured as the difference between the market value of the firm and the book value of tangible assets all normalized by sales as a result thomadakis argued that industry concentration plays a role in the determination of excess profits from currently held assets and those expected from the firm s investment options p 185 in contrast lindenberg and ross 1981 reported no significant relation between concentration and tobin s q ratio measured as the ratio of the market value of the firm to the replacement cost of tangible assets this result disputes thomadakis s findings and a purely structuralist interpretation of economic profits according to lindenberg and ross market power may or may not be evident in highly concentrated markets since high q s can occur in concentrated or unconcentrated markets and conversely low q s indicating no significant market power can occur in markets that have high degrees of concentration p 28

dynamic inventory rationing for systems with multiple demand classes and general demand processes we consider the dynamic rationing problem for inventory systems with multiple demand classes and general demand processes we assume that backorders are allowed our aim is to find the threshold values for this dynamic rationing policy for single period systems dynamic critical level policy is developed and the detailed cost approximation subject to this policy is derived for multiperiod systems a dynamic rationing policy with periodic review is proposed the numerical study shows that our dynamic critical level policies are close to being optimal for various parameter settings

inventory policies for systems with stochastic and deterministic demand we consider a periodic review inventory system with demand arriving simultaneously from a deterministic source and a random source the deterministic demand has to be satisfied immediately and the stochastic demand can be backordered assuming that the stochastic demand is never backlogged if there is stock in the system we prove that a modified s s policy is optimal under general conditions if there is a setup cost if there is a smoothing cost instead of the setup cost we observe that the problem corresponds to a standard model with one source of demand

production and inventory control of a single product assemble to order system with multiple customer classes we consider the optimal production and inventory control of an assemble to order system with m components one end product and n customer classes a control policy specifies when to produce each component and whenever an order is placed whether or not to satisfy it from on hand inventory we formulate the problem as a markov decision process and characterize the structure of an optimal policy we show that a base stock production policy is optimal but the base stock level for each component is dynamic and depends on the inventory level of all other components more specifically it is nondecreasing we show that the optimal inventory allocation for each component is a rationing policy with different rationing levels for different demand classes the rationing levels for each component are dynamic and also nondecreasing in the inventory level of all other components we compare the performance of the optimal policy to heuristic policies including the commonly used base stock policy with fixed base stock levels and find them to perform surprisingly well especially for systems with lost sales

an income strategy approach to the positive theory of accounting standard setting choice abstract this paper is designed to provide additional evidence on the positive theory of accounting policy choice by combining individual accounting principles into firm income strategies these strategies were the dependent variable in a probit analysis where the independent variables were size management compensation industry concentration ratio systematic risk capital intensity and the total debt to total asset ratio the results indicate that four of these factors size management compensation concentration ratio and the total debt to total asset ratio have a significant association with the choice of a firm s income strategy this test provides strong evidence consistent with the positive theory of accounting standard setting choice we also present evidence that smaller firms and or firms in less concentrated industries do not appear to make accounting policy choice decisions that are consistent with this theory

a hybrid inventory policy with split delivery under regular and surge demand abstract this paper proposes a hybrid inventory policy with split delivery under regular and surge demand the combination of regular and surge demand can be observed in many areas such as healthcare inventory and humanitarian supply chain management the arrival rate of regular demand is typically higher than the arrival rate of surge demand whereas the volume of regular demand is typically lower than the volume of surge demand this paper proposes an inventory management model that considers both emergency and regular replenishments corresponding to both demand patterns the equilibrium equations developed for this model are based on the level crossing theory these equations are used to develop a search based heuristics to identify near optimal inventory management policies numerical results show that the proposed hybrid inventory policy with split delivery outperforms similar hybrid inventory policy without split delivery when holding and shortage costs are relatively low

evaluating q as an alternative to the rate of return in measuring profitability the ratio of a firm s market value to its replace ment cost q is often used to measure firms profitability the use of q is increasin g in large part because of the growing realization that errors in evaluating firms capital assets may cause errors in estimates of the accounting rate of return r the same objection however applies t o q this paper reports the results of monte carlo experiments designed to determine whether q is superior to r errors in both q and r are large and potentially serious but do not render either measure useless copyright 1988 by mit press

networks in the modern economy mexican migrants in the u s labor market this paper attempts to identify job networks among mexican migrants in the u s labor market the empirical analysis uses data on migration patterns and labor market outcomes based on a sample of individuals belonging to multiple origin communities in mexico over a long period of time each community s network is measured by the proportion of the sampled individuals who are located at the destination the united states in any year we verify that the same individual is more likely to be employed and to hold a higher paying nonagricultural job when his network is exogenously larger by including individual fixed effects in the employment and occupation regressions and by using rainfall in the origin community as an instrument for the size of the network at the destination

component commonality with service level requirements this paper extends recent results of baker et al baker k r m j magazine h l w nuttle 1986 the effect of commonality on safety stocks in a simple inventory model management sci 32 982 988 in understanding the impact of component commonality on stocking levels under service level constraints a model is formulated for an arbitrary number of products with general joint demand distribution the results obtained are not all intuitive while utilizing commonality is beneficial nothing general can be said about the resulting change in the components stock levels when the cost structure is of a particular simple form though some interesting general patterns do emerge we also discuss the case of using a service level measure where rationing of common components might be required and characterize the implied rationing rule

inventory sharing and rationing in decentralized dealer networks an increasing number of manufacturers have started to pursue a strategy that promotes inventory sharing among the dealers in their distribution network in this paper we analyze a decentralized dealer network in which each independent dealer is given the flexibility to share his inventory we model inventory sharing as a multiple demand classes problem in which each dealer faces his own customer demand with high priority and inventory sharing requests from other dealers with low priority assuming that each dealer uses a base stock and threshold rationing policy for his inventory stocking and inventory sharing decisions we explicitly model the interactions between the dealers through inventory sharing and obtain aclosed form cost function for each dealer based on the steady state distribution of the inventory levels at the two dealers we then provide a detailed supermodularity analysis of the inventory sharing and inventory rationing game in which each dealer has a two dimensional strategy set stocking level and rationing level we show that the full sharing game in which dealers precommit to sharing all of their on hand inventory and the fixed sharing level game in which dealers precommit to sharing a portion of their on hand inventory are supermodular and thus a pure strategy nash equilibrium is guaranteed to exist for the rationing game in which dealers precommit to their stocking levels we show that there exists a dominant strategy equilibrium on the dealers sharing rationing levels finally a comprehensive computational study is conducted to highlight the impact of the manufacturer s incentives subsidies and or transshipment fees on the dealers sharing behavior

how do u s visa policies affect unauthorized immigration abstract how would increasing the number of visas available to potential migrants affect unauthorized immigration from mexico to the u s current u s policy bans people who are deported from receiving legal status for a period of time this policy aims to serve as an additional deterrent to unauthorized immigration but may be ineffective given that most potential mexican migrants have an extremely low probability of ever being able to legally move to the u s we develop a dynamic discrete location choice model which we estimate using data from the mexican migration project and consider various counterfactual policies that vary the intensity of enforcement and access to work visas we find that legal entry bans for deported individuals are ineffective at current rates of legal immigration but that increased legalization rates would amplify the deterrent effects of deportation we also show that a temporary work visa program would yield similar deterrent effects as an increase in permanent legalization without resulting in very large increases in the total stock of migrants residing in the u s these findings have important implications for structuring future immigration reforms

using imperfect advance demand information in ordering and rationing decisions in this paper we consider an inventory problem with two demand classes having different priorities the appropriate policy of rationing the available stock i e reserving some stock for meeting prospective future demand of preferred customers at the expense of deliberately losing some of the currently materialized demand of lower demand class es relies on the estimation of the future demand utilizing current signals on future demand which we refer to as imperfect advance demand information adi decreases uncertainty on future demand and may help to make better decisions on when to start rejecting lower class demand we develop a model that incorporates imperfect adi with inventory ordering replenishment decision and rationing available stock in a two period setting we show some structural properties solve the rationing problem and propose solution methods based on monte carlo simulation for the ordering problem we conduct numerical tests to measure the impact of system parameters on the expected value of imperfect adi and provide useful managerial insights

dynamic inventory rationing with mixed backorders and lost sales abstract customers may react differently when stockouts occur in this paper we investigate the rationing policy for an inventory system with a mixture of demand classes of backorder type and lost sales type since the penalty cost of backorders varies with time the priorities of demand classes also alter with time this totally changes the problem structure compared with the classic rationing models a dynamic rationing policy is studied in this paper by considering the dynamics of demand priorities a markov decision model is developed to obtain the optimal dynamic rationing levels for multiple demand classes the results indicate that between the priority switching points rationing levels often exhibit different patterns for lost sales demand classes the rationing levels always decrease as the remaining time approaches to zero for backorder demand classes the rationing levels increase in some parts due to declining of the priorities the rationing levels of all demand classes finally decline to zero to reduce the inventory holding cost the application of dynamic rationing is further extended from a single period model to a multi period s t model where unit cost has to be included the optimal ordering policy is proved to be a myopic base stock policy and the dynamic rationing policy in the single period model can still be applied with modified time independent penalty costs for lost sales classes to overcome the computational complexity a heuristic dynamic rationing policy is introduced due to its good outcome implementing such a heuristic dynamic rationing policy can be a practical solution for inventory system with mixed backorders and lost sales in order to enhance the system performance

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