an economic order quantity model for an imperfect production process with entropy cost abstract among the assumptions of the classical economic order quantity eoq model is that all units that are purchased or produced are of perfect quality however this is frequently unrealistic since production processes deteriorate resulting in the production of defective products requiring rework some recent studies suggest that production systems performance might be improved by applying the first and second laws of thermodynamics to reduce system entropy or disorder this paper applies the concept of entropy cost to extend the classical eoq model under the assumptions of perfect and imperfect quality mathematical models are developed and numerical examples illustrating the solution procedure are provided accounting for entropy cost suggests that order quantities should be larger than the figures derived from the classical eoq model

optimal lot sizing for an unreliable production system based on net present value approach abstract the paper considers the net present value npv approach to determine the economic manufacturing quantities for an unreliable production system over an infinite planning horizon the npv of the expected total cost is obtained under general failure time and general repair time distributions and its asymptotic characteristics are examined by perturbation of the instantaneous discount rate the criteria for the existence and uniqueness of the optimal production time lot size are derived under exponential failure and constant zero repair time the performance of the npv model is compared with the traditional long run average cost model in terms of the npv of the expected total cost based on the optimal decisions of the two models from numerical experiments it is observed that the decision based on the average cost can be 10 worse than the decision based on the npv depending upon the machine failure rate

short comments on technical note the eoq and epq models with shortages derived without derivatives abstract we study the paper of ronald yang and chu that was recently published in the international journal of production economics to find the optimal solution for the eoq and epq models without derivatives we will offer a simple algebraic method to replace their sophisticated algebraic skill and then we point out a possible direction for further research

note on economic production quantity model for items with imperfect quality a practical approach abstract in this note we present a simple approach for determining the economic production quantity for an item with imperfect quality we compare the results based on the simple approach with the optimal method for determining the lot size and show that almost optimal results are obtained using the simple approach

too many to fail evidence of regulatory forbearance when the banking sector is weak this paper studies bank failures in 21 emerging market countries in the 1990s by using a competing risk hazard model for bank survival we show that a government is less likely to take over or close a failing bank if the banking system is weak this too many to fail effect is robust to controlling for macroeconomic factors financial crises the too big to fail effect domestic financial development and concerns due to systemic risk and information spillovers the paper also shows that the too many to fail effect is stronger for larger banks and when there is a large government budget deficit

location and competition in retail banking abstract we investigate the impact of banking deregulation during the 1990s on consumer welfare we estimate a spatial model of consumer demand for retail bank deposits that explicitly accounts for consumer disutility from distance traveled this is important given the substantial changes in banks branch networks observed in the data our model indicates that cross price elasticities between banks whose branches are close to consumers close banks are larger than those between far banks and more than double the cross price elasticity of close banks with respect to far banks we distinguish between thrifts and other banks and find that within thrift competitive effects are stronger than within bank effects or those between thrifts and banks we use our estimates to predict the effect of changes in market structure on consumer welfare following the branching deregulation of the riegle neal act of 1994 our results indicate that the median household gained around 60 per year from the changes approximately two thirds of the gains come from within market changes in market structure the gains were greater in markets with high initial numbers of banks than elsewhere

an eoq model with stock dependent demand shortage inflation and time discounting abstract this paper develops a finite time horizon deterministic economic order quantity eoq inventory model with shortages where the demand rate at any instant depends on the on hand inventory stock level at that instant the effects of inflation and the time value of money are taken into account considering two separate inflation rates namely the internal company inflation rate and the external general economy inflation rate the results are discussed with a numerical example and particular case of the model is discussed in brief a sensitivity analysis of the optimal solution with respect to the parameters of the system is carried out

replenishment and pricing policy for deteriorating items taking into account the time value of money abstract a deteriorating inventory model taking into account the time value of money is developed for a deterministic inventory system with price dependent demand this study applies the discounted cash flows dcf approach for problem analysis a heuristic approach is presented to derive the near optimal replenishment and pricing policy that tries to maximize the total net present value profit a numerical example is implemented to illustrate the theory

psychological factors and stock option exercise we investigate stock option exercise decisions by over 50 000 employees at seven corporations controlling for economic factors psychological factors influence exercise consistent with psychological models of beliefs employees exercise in response to stock price trends exercise is positively related to stock returns during the preceding month and negatively related to returns over longer horizons consistent with psychological models of values that include reference points employee exercise activity roughly doubles when the stock price exceeds the maximum price attained during the previous year

efficient lot sizing under a differential transportation cost structure for serially distributed warehouses abstract a major cost element in the logistics of distributed warehousing is transportation cost in most practical systems the transportation costs are volume dependent the unit transportation costs are usually determined differentially among intervals of shipment volumes while the unit cost is constant over an interval it follows a stepwise declining pattern from an interval to the next higher interval of shipment volumes this structure is analogous to that of quantity discounted inventory systems we consider a single product serial warehousing system operating under the differential transportation costs and the traditional holding and ordering costs external demand occurs at the final stage at a constant continuous rate demand must be met on time over an infinite horizon under continuous review the objective is to determine the ordering lot size for each warehouse such that the long run average cost is minimized we model the above problem and establish its structural properties we first consider two level differential transportation cost structures and develop efficient algorithms to obtain a best integer ratio and optimal powers of two policies next we consider multilevel cost structures and develop a hypercube characterization of the solution space efficient algorithms to yield a best integer ratio and powers of two policies using the hypercube model and a relaxation approach using the two level model are developed extensive computational studies with the algorithms reveal that the proposed modeling and algorithmic approach is both viable and efficient in solving practical distribution problems conclusions and direction for future research are presented

efficient inventory control for imperfect quality items in this paper we present a general eoq model for items that are subject to inspection for imperfect quality each lot that is delivered to the sorting facility undertakes a 100 per cent screening and the percentage of defective items per lot reduces according to a learning curve the generality of the model is viewed as important both from an academic and practitioner perspective the mathematical formulation considers arbitrary functions of time that allow the decision maker to assess the consequences of a diverse range of strategies by employing a single inventory model a rigorous methodology is utilised to show that the solution is a unique and global optimal and a general step by step solution procedure is presented for continuous intra cycle periodic review applications the value of the temperature history and flow time through the supply chain is also used to determine an efficient policy furthermore coordination mechanisms that may affect the supplier and the retailer are explored to improve inventory control at both echelons the paper provides illustrative examples that demonstrate the application of the theoretical model in different settings and lead to the generation of interesting managerial insights

an eoq model for deteriorating items with a linear trend in demand and shortages in all cycles abstract we consider here the inventory replenishment problem over a finite time horizon for a deteriorating item with a linear trend in demand equal replenishment cycles and shortage in every cycle the reorder number the interval between two successive reorders and the shortage intervals are all determined in an optimal manner so as to minimize the average system cost the advantage of allowing shortage in all cycles is illustrated with a numerical example

ford whitman harris and the economic order quantity model ford whitman harris first presented the familiar economic order quantity eoq model in a paper published in 1913 even though harris s original paper was disseminated widely it apparently was unnoticed for many years before its rediscovery in 1988 during this period much confusion developed over the origin of the eoq model this paper explores the early literature on this model and traces the evolution of the confusion it also sketches the remarkable life of harris who made contributions as an engineer inventor author and patent attorney even though he received no formal education beyond high school harris s original 1913 essay is reprinted following this paper

deteriorating inventory model with quantity discount pricing and partial backordering inventory models with quantity discount pricing and partial backordering although common in practice have received very little attention from researchers the objective of this study is to develop a deterministic inventory model with quantity discount pricing and partial backordering when the product in stock deteriorates with time most retailers make pricing decisions of their products at certain times of the year and these decisions affect demand in this study the demand rate is assumed to decrease as price for the product increases unlike traditional inventory models that seek to minimize cost the objective of this study is to maximize profit the findings of this study are particularly relevant to retailers of deteriorating products in a competitive environment a numerical example is given to illustrate the theory

the eoq with backlogging derived without derivatives abstract in previous work the eoq formula without consideration to backlogging has been given a derivation without reference to the use of derivatives neither for necessary conditions nor for second order sufficient conditions furthermore this algebraic derivation immediately provided the value of the average cost function in optimum this paper extends the previous result to the eoq formula taking the backlogging case into consideration it is shown that a similar derivation immediately provides the corresponding results for this case

investments in modern production technology and the cash flow oriented epq model in this study we analyze investments in setup and production processes in the context of the traditional inventory problem the comparison of the results of a cash flow and a cost oriented model suggests the use of the net present value as a decision criterion the analysis shows that an additional investment which reduces setup cost decreases the optimal capital investment necessary to reduce production cost and vice versa an investment which increases the production rate however may increase or decrease the capital expenditure of an investment in the setup process

competitive pricing behavior in the auto market a structural analysis in a competitive marketplace the effectiveness of any element of the marketing mix is determined not only by its absolute value but also by its relative value with respect to the competition for example the effectiveness of a price cut in increasing demand is critically related to competitors reaction to the price change managers therefore need to know the nature of competitive interactions among firms in this paper we take a theory driven empirical approach to gain a deeper understanding of the competitive pricing behavior in the u s auto market the ability motivation paradigm posits that a firm needs both the ability and the motivation to succeed in implementing a strategy boulding and staelin 1995 we use arguments from the game theoretic literature to understand firm motivation and abilities in different segments of the auto market we then combine these insights from the game theoretic literature and the ability motivation paradigm to develop hypotheses about competition in different segments of the u s auto market to test our hypotheses of competitive behavior we estimate a structural model that disentangles the competition effect from the demand and cost effects on prices the theory of repeated games predicts that firms with a long run profitability objective will try to sustain cooperative pricing behavior as a stable equilibrium when conditions permit for example markets with high concentration and stable market environments are favorable for sustaining cooperative behavior and therefore provide firms with the ability to cooperate the theory of switching costs suggests that in markets in which a firm s current customers tend to be loyal firms have a motivation to compete very aggressively for new customers recognizing the positive benefits of loyalty from the customer base in the long run as consumer loyalty in the market increases the gains from increasing market share by means of aggressive competitive behavior are more than offset by losses in profit margins firms therefore have the motivation to price cooperatively empirically we find aggressive behavior in the minicom pact and subcompact segments cooperative behavior in the compact and midsize segments and bertrand behavior in the full size segment these findings are consistent with our theory based hypotheses about competition in different segments in estimating a structural model of the auto market we address several methodological issues a particular difficulty is the large number of car models in the u s auto market existing studies have inferred competitive behavior only in markets with two to four products they also use relatively simple functional forms of demand to facilitate easy estimation functional forms of demand however impose structure on cross elasticities between products such structure when inappropriate can bias the estimates of competitive interaction we therefore use the random coefficients logit demand model to allow flexibility in cross elasticities we also use recent advances in new empirical industrial organization neio to extend structural estimation of competitive behavior to markets with a large number of products we use the simulation based estimation approach developed by berry et al 1995 to estimate our model a frequent criticism of the neio approach is that its focus on industry specific studies limits the generalizability of its findings in this study we retain the advantages of neio methods but partially address the issue of generalizability by analyzing competitive behavior in multiple segments within the auto industry to see whether there is a consistent pattern that can be explained by theory theoretical modelers can use our results to judge the appropriateness of their models in predicting competitive outcomes for the markets that they analyze a by product of our analysis is that we also get estimates of demand and cost apart from competitive interactions for the market managers can use these estimates to perform what if analysis they can answer questions about what prices to charge when a new product is introduced or when an existing product s characteristics are changed

an economic order quantity model with defective items and shortages abstract the fundamental assumption of an economic order quantity eoq model is that 100 of items in an ordered lot are perfect this assumption is not always pertinent for production processes because of process deterioration or other factors this paper develops an eoq model for that each ordered lot contains some defective items and shortages backordered it is assumed that 100 of each lot are screened to separate good and defective items which are collection of imperfect quality and scrap items the effect of percentage defective on optimal solution is studied while numerical examples are provided for the developed model

an algorithm to determine the eoq for deteriorating items with shortage and a linear trend in demand abstract in 1991 professors goswami and chaudhuri considered the inventory replenishment policy over a fixed planning period for a deteriorating item having a deterministic demand pattern with a linear trend and shortages basically they concentrated on the establishment of the inventory model but did not present a concrete algorithm to solve it this paper complements the shortcoming of goswami and chaudhuri s paper we first show that the total cost function of goswami and chaudhuri is convex subsequently with the convexity an algorithm to determine the number of reorders the interval between two successive reorders and the shortage intervals over a finite time horizon in an optimal manner is developed many numerical examples illustrate how the algorithm works

taxation and executive compensation evidence from stock options abstract understanding the effects of taxes on executive compensation provides insight into the process determining this compensation and is a key input to top income tax rate policy a 2010 tax reform in canada which greatly increased the effective tax rate on stock option compensation for a subset of firms provides a natural experiment with which to address this issue difference in differences estimates suggest that this tax increase resulted in an immediate reduction in both stock option grants and the fraction of total compensation made up of stock options with limited if any substitution towards other components of compensation

an eoq model with noninstantaneous receipt and exponentially deteriorating items under two level trade credit abstract this paper considers the impact of the trade credit policy on the classical economic production quantity epq model for an item subject to exponential decays essentially this study focuses on an exponentially deteriorating item under the conditions of the retailer receiving the supplier trade credit and providing the customer trade credit simultaneously so as to minimize the average total cost a theorem is developed to determine the optimal replenishment policies the main contribution to literature is the inclusion of the latter type of payment delay finally through numerical examples sensitive analysis shows the influence of key model parameters

the end of the robinson patman act evidence from legal case data the robinson patman act rp an antitrust statute aimed at protecting small businesses limits price setting in distribution channels to avoid costly penalties under rp managers take a variety of precautions when pricing to retailers and wholesalers but how likely is a court to find a defendant guilty of violating the rp we find that this likelihood has dropped drastically as a result of recent supreme court rulings from more than 1 in 3 before 1993 to less than 1 in 20 for the period 2006 2010 the analysis also points to an increased success of the no harm to competition defense which reflects the view that the courts have raised the hurdle for plaintiffs to establish competitive harm finally our results indicate that smaller plaintiffs over time have fared worse than larger ones a trend that challenges the notion that rp protects small businesses

economic lot size model for price dependent demand under quantity and freight discounts abstract previous studies have developed procedures which determine optimal lot size and selling price when demand depends on price and all unit quantity discounts are offered further recent studies have addressed the concepts of quantity and freight discounts for constant demand in this paper we incorporate quantity and freight discounts in inventory decision making when demand rather than being constant is considered to be dependent upon price an algorithm is developed to determine the optimal lot size and selling price for a class of demand functions including constant price elasticity and linear demand a numerical example is provided to illustrate the model and a computer program is developed to implement the model derived in the paper

the deterministic eoq with partial backordering a new approach previous authors have shown that if demand that cannot be filled from stock is partially backordered then using the full backordering model or assuming that all stockouts will result in lost sales can lead to substantial increases in cost relative to using a model that specifically recognizes the percentage of the stockouts that will be backordered the models that these authors developed resulted in procedures or equations that are relatively difficult to use in this paper we take a different approach to modeling the deterministic eoq with partial backordering that results in equations that are more like the comparable equations for the basic eoq and its full backordering extension

demand fluctuations in the ready mix concrete industry i investigate the role of demand shocks in the ready mix concrete industry using census data on more than 15 000 plants i estimate a model of investment and entry in oligopolistic markets these estimates are used to simulate the effect of eliminating short term local demand changes a policy of smoothing the volatility of demand has a market expansion effect the model predicts a 39 increase in the number of plants in the industry since bigger markets have both more plants and larger plants a demand smoothing fiscal policy would increase the share of large plants by 20 finally the policy of smoothing demand reduces entry and exit by 25 but has no effect on the rate at which firms change their size

discounted costs obsolescence and planned stockouts with the eoq formula abstract in this paper we propose a simple economic order quantity for a class of inventory management problems concerning items with a short and stochastic lifetime the analysis is relevant to the management of items in industries subject to fast technological progress where the obsolescence rate is large the approach is performed in the framework of the total discounted cost criterion a new economic order quantity is computed it may turn out to be significantly smaller than the one given by wilson formula finally we show that a policy maker who faces the risk of obsolescence can plan stockouts if sufficiently many customers accept late delivery

the effect of information on product quality evidence from restaurant hygiene grade cards this study examines the effect of an increase in product quality information to consumers on e rms choices of product quality in 1998 los angeles county introduced hygiene quality grade cards to be displayed in restaurant windows we show that the grade cards cause i restaurant health inspection scores to increase ii consumer demand to become sensitive to changes in restaurants hygiene quality and iii the number of foodborne illness hospitalizations to decrease we also provide evidence that this improvement in health outcomes is not fully explained by consumers substituting from poor hygiene restaurants to good hygiene restaurants these results imply that the grade cards cause restaurants to make hygiene quality improvements

an inventory model with deteriorating items under inflation when a delay in payment is permissible abstract this study develops an inventory model for initial stock dependent consumption rate when a delay in payment is permissible in the inventory model shortages are not allowed the effect of the inflation rate deterioration rate initial stock dependent consumption rate and delay in payment are discussed in the study mathematical models are also derived under two different circumstances i e case i the credit period is less than or equal to the cycle time for settling the account and case ii the credit period is greater than the cycle time for settling the account besides expressions for an inventory system s total cost are derived for these two cases moreover a computational procedure and gino lasdon et al acm transactions mathematical software 4 1978 34 50 are proposed to obtain the optimal order size and cycle time the results can help managers determine the optimal total cost finally a numerical example demonstrates the applicability of the proposed model

the effect of marginal tax rates on taxable income a panel study of the 1988 tax flattening in canada abstract federal tax reform in 1988 flattened the canadian personal income tax schedule changing the marginal tax rates for many individuals using methods similar to those applied by auten and carroll rev econ 81 4 1999 681 in the study of the effects of the 1986 u s tax reform act we estimate the responsiveness of income to changes in taxes to be substantially smaller in canada however we find evidence of a much higher response in self employment income in the labor income of seniors and from those with high incomes

cumulative staircase considerations for dynamic lotsizing when backlogging is allowed abstract the dynamic lotsizing problem concerns the determination of optimal batch quantities when given required amounts appear at discrete points in time the standard formulation assumes that no shortages are allowed and that replenishments are made instantaneously for the case when no shortage is allowed previously it has been demonstrated that the inner corner condition for an optimal production plan in continuous time reduces the number of possible replenishment times to a finite set of given points at which either a replenishment is made or not the problem is thus turned into choosing from a set of zero one decisions with 2 n 1 alternatives of which at least one solution must be optimal where n is the number of requirement events recently the instantaneous replenishment assumption has been replaced by allowing for a finite production rate which turned the inner corner condition into a condition of tangency between the cumulative demand staircase and cumulative production in this paper we investigate relationships between optimal cumulative production and cumulative demand when backlogging is permitted the production rate is assumed constant and cumulative production will then be a set of consecutive ramps cumulative demand is a given staircase function the net present value npv principle is applied assuming a fixed setup cost for each ramp a unit production cost for each item produced and a unit revenue for each item sold at the time it is delivered among other results it is shown that optimal cumulative production necessarily intersects the demand staircase instead of having 2 n 1 production staircases as candidates for optimality there are 2 n 1 production structures as candidates these are made up of sequences of batches of which the set of batches may be optimised individually also is shown that the npv of each batch has a unique timing maximum and behaves initially in a concave way and ends as convex results for the average cost approach are obtained from a zeroth first order approximation of the objective function npv

the optimal inventory policies under permissible delay in payments depending on the ordering quantity abstract this paper deals with the problem of determining the economic order quantity under conditions of permissible delay in payments the delay in payments depends on the quantity ordered when the order quantity is less than the quantity at which the delay in payments is permitted the payment for the item must be made immediately otherwise the fixed trade credit period is permitted the minimization of the total variable cost per unit of time is taken as the objective function an algorithm to determine the economic order quantity is developed the results obtained in this paper generalize some already published results

an eoq model under retailer partial trade credit policy in supply chain abstract the main purpose of this paper is to investigate the retailer s inventory policy under two levels of trade credit to reflect the supply chain management situation in this paper we assume that the retailer has the powerful decision making right so we extend the assumption that the retailer can obtain the full trade credit offered by the supplier and the retailer just offers the partial trade credit to his her customer then we investigate the retailer s inventory system as a cost minimization problem to determine the retailer s optimal inventory policy under the supply chain management two easy to use theorems are developed to efficiently determine the optimal inventory policy for the retailer we deduce some previously published results of other researchers as special cases finally numerical examples are given to illustrate the theorems and obtain a lot of managerial phenomena

a note on how to compute economic order quantities without derivatives by cost comparisons abstract a different approach to obtain the economic order quantity and several extensions without taking derivatives is presented in contrast to previous contributions to this discussion cost comparisons in a finite horizon and analyzing the limiting behavior are used rather than algebraic manipulations of the average cost function and comparison of coefficients

the eqq model with stochastic demand and discounting abstract we generalize bather s eqq model with stochastic demand to the case with discounting we consider two cases one with and one without demand backlogging important implications of discounting are investigated useful insights and formulas are provided

including sustainability criteria into inventory models research on sustainability performance has considerably enriched operations management literature in recent years however work with quantitative models is still scarce this paper contributes by revisiting classical inventory methods taking sustainability concerns into account we believe that reducing all aspects of sustainable development to a single objective is not desirable we thus reformulate the classical economic order quantity model as a multiobjective problem we refer to this model as the sustainable order quantity model then a multi echelon extension of the sustainable order quantity model is studied for both models the set of efficient solutions pareto optimal solutions is analytically characterized these results are used to provide some insights about the effectiveness of different regulatory policies to control carbon emissions we also use an interactive procedure that allows the decision maker to quickly identify the best option among these solutions the proposed interactive procedure is a new combination of multi criteria decision analysis techniques

a century of evolution from harris s basic lot size model survey and research agenda abstract determining the economic lot size has always represented one of the most important issues in production planning this problem has long attracted the attention of researchers and several models have been developed to meet requirements at minimum cost in this paper we explore and discuss the evolution of these models during one hundred years of history starting from the basic model developed by harris in 1913 up to today following harris s work a number of researchers have devised extensions that incorporate additional considerations the evolution of eoq theory strongly reflects the development of industrial systems over the past century here we outline all the research areas faced in the past by conducting a holistic analysis of 219 selected journal papers and trying to give a comprehensive view of past work on the eoq problem finally a new research agenda is proposed and discussed

volunteering to be taxed business improvement districts and the extra governmental provision of public safety abstract when the median voter s preference sets the level of local public goods some voters are left unsatisfied is there an institution by which subsets of voters can resolve the collective action problem and increase the local provision of public goods if so what are the consequences in response to problems such as crime and vandalism neighborhood property owners have established business improvement districts bids to provide local public goods when a bid is approved by a majority of property owners in a neighborhood state law makes contributions to the bid budget mandatory this resolution of the neighborhood s collective action problem reduces crime bids in the city of los angeles are robustly associated with crime declines of 6 to 10 indeed crime falls regardless of estimation technique fixed effects comparing bids to neighborhoods that considered but did not adopt bids using propensity score matching and comparing bids to their neighbors strikingly these declines are purchased cheaply attributing all bid expenditure to violent crime reduction and thus ignoring the impact of bid expenditure on many quality of life crimes bids spend 21 000 to avert one violent crime this higher bound estimate is substantially lower than the 57 000 social cost of a violent crime

economic production quantity for fuzzy demand quantity and fuzzy production quantity abstract in the fundamental production inventory model in order to solve the economic production quantity epq per cycle we always fix both the demand quantity and the production quantity per day but in the real situation both of them probably will have little disturbances every day therefore we should fuzzify both of them to solve the ecoomic production quantity q per cycle the purpose of this paper is to investigate a computing schema for the epq in the fuzzy sense we find that after defuzzification the total cost is although slightly higher than in the crisp model however it permits better use of the epq in the crisp arising with little disturbances in the production and demand

managing carbon footprints in inventory management abstract there is a broad consensus that mankind must reduce carbon emissions to mitigate global warming it is generally accepted that carbon emission trading is one of the most effective market based mechanisms to curb the amount of carbon emissions this paper investigates how firms manage carbon footprints in inventory management under the carbon emission trading mechanism we derive the optimal order quantity and analytically and numerically examine the impacts of carbon trade carbon price and carbon cap on order decisions carbon emissions and total cost we make interesting observations from the numerical examples and provide managerial insights from the analytical results

taxes and executive stock options abstract in the sixties the qualified stock option was the predominant form of long term incentive compensation contract for major industrial firms in the u s in the early seventies these same firms replaced their tax qualified stock option plans with non qualified sttock options and later modified these plans to include a variety of new contingent compensation arrangements some of which were based on accounting numbers instead of stock prices this paper develops the hypothesis that tax considerations play an important role in explaining the form of compensation contracts the pattern and timing of changes in the compensation plans of the top 100 industrial firms provides evidence consistent with the tax hypothesis

numerical computation of inventory policies based on the eoq σx value for order point systems abstract this paper examines the numerical computation of two control parameters order size and order point in the well known inventory control model an s q system with a safety stock strategy the aim of the paper is to show that the eoq x value is both sufficient for controlling the system and essential for the economic consequences of using approximations in computations of optimal policies in view of the evidence from a number of studies showing that firms use of statistical inventory control lags far behind academic interest in the area this is also an important aspect the determination of optimal values for the control variables even in this very simple inventory control system is a complex task and therefore not suited to practical implementation where one or more of the following issues are neglected the interdependence of order size and order point the difference between stock on hand and net stock and the excess stockout included in the next period we use the determination of optimal values for the control variables as a framework to evaluate the economic consequences of these approximations applied in pratical inventory control

deterministic models of perishable inventory with stock dependent demand rate and nonlinear holding cost this paper deals with an extended eoq type inventory model for a perishable product where the demand rate is a function of the on hand inventory the traditional parameters of unit item cost and ordering cost are kept constant but the holding cost is treated as i a nonlinear function of the length of time for which the item is held in stock and ii a functional form of the amount of the on hand inventory the approximate optimal solution in both the cases are derived computational results are presented indicating the effects of nonlinearity in holding costs

economic lot sizing with learning and continuous time discounting is it significant abstract learning curves are a means of representing continuous improvement in firms such improvements bring savings in production costs this may also allow smaller batches to be produced more frequently and hence bring further savings in holding costs earlier research advocated that for more realistic modelling of inventory problems the holding cost should be evaluated means of the internal discount rate of the firm c van deft j p vail international journal of production economics 44 1996 255 265 this paper examines whether when learning is considered it is reasonable to ignore the effect of continuous time discounting of costs by investigating the effect of learning and time discounting both on the economic manufacturing quantity and minimum total inventory cost numerical examples are provided to illustrate the solution procedure for the mathematical model developed although the analysis yields different economic order quantities the difference in cost from the quantities derived using wilson lot size formula is not significant

an eoq lot sizing model with random supplier capacity abstract this paper presents a general formulation of the inventory lot sizing model with random supplier capacity under the eoq framework for a general capacity distribution we show that the expected cost per unit of time is a unimodal function and pseudo convex in the ordering quantity moreover we derive some simple data dependent bounds for both optimal lot size and expected cost per unit of time in order to illustrate the general model three types of distributions for the random capacity are analyzed as special cases these are the uniform exponential and truncated normal distributions for each of these distributions we find that the maximum cost penalty of using the eoq lot size instead of the optimal one is almost negligible not greater than 0 52 1 81 and 0 91 for the uniform exponential and truncated normal distributions respectively in addition we extend the general model to allow for the presence of defective units in the quantity received from the supplier it is shown that this extra randomness does not affect the optimal ordering policy for the original model

the deterministic eoq and epq with partial backordering at a rate that is linearly dependent on the time to delivery abstract our original models for the eoq and epq with partial backordering assumed that the backordering rate is a constant in this paper we extend those models to allow to increase linearly as the time until delivery decreases we show how those previous models can be adapted to find the optimal decision variable values for this new assumption and develop for each model type a condition that the initial value of must meet for partial backordering to be optimal

environmentally responsible inventory models non classical models for a non classical era abstract mathematical models of inventory typically include the three inventory associated costs of surplus shortage and ordering these classic inventory models are then analysed so as to choose inventory parameters that usually minimise the total cost of operating the inventory system being investigated unfortunately classic inventory models do not provide a meaningful basis for analysing many real and increasingly important practical inventory problems and situations it is therefore not surprising that over recent years several authors have discussed these issues in broad terms and suggested that a new paradigm needs to be developed this paper develops some specific aspects of this discussion in particular the paper identifies a range of inventory problems that are not covered appropriately by traditional inventory analysis one of these is to design responsible inventory systems i e systems that reflect the needs of the environment the paper then examines the importance of inventory planning to the environment in greater detail for example packaging is important not only because of its costs and the protection that it provides to the inventory items but also because of its eventual effects on the environment in terms of the use of resources and potential landfill for similar reasons waste which can result from poor inventory management is highly important the location of stores is important because location affects transport costs thus the influence of the secondary aspects of most inventory models packaging waste and location are important but even more important are the inter relations with the total system in particular the location of the manufacturing plants and the effect that inventory planning has on the logistics chain potentially have considerable environmental implications inventory is part of a wider system however until the cost charged for an activity reflects the true environmental cost of that activity it is likely that decisions will be made on the basis of erroneous data in that situation we are faced with either determining the environmental cost of specific actions or to use environmental costs that are somewhat contrived in which case it may be more sensible to use very different performance measures and models the paper discusses these ideas and ways in which inventory policies may reassure us with our environmental concerns

what happens when you tax the rich evidence from executive compensation this paper examines the responsiveness of taxable income to changes in marginal tax rates using detailed compensation data on several thousand corporate executives from 1991 to 1995 the data confirm that the higher marginal rates of 1993 led to a significant decline in taxable income indeed this small group of executives may account for as much as 20 percent of the aggregate change in wage and salary income for approximately the one million richest taxpayers over this time period one person alone can account for more than 2 percent the decline however is almost entirely a short run shift in the timing of compensation rather than a permanent reduction in taxable income the short run elasticity of taxable income with respect to the net of tax share exceeds one in this sample but the elasticity after one year is at most 0 4 and probably closer to zero breaking out the tax responsiveness of different types of compensation shows that the large short run responses come almost entirely from a large inc

production planning with discounting and stochastic demands abstract a general continuous review production planning problem with stochastic demand is considered conditions under which the stochastic problem may be correctly solved using an equivalent deterministic problem are developed this deterministic problem is known to have the same solution as the stochastic problem moreover conditions are established under which the deterministic equivalent problem differs from a commonly used deterministic approximation to the problem only in the interest rate used in discounting thus solving the stochastic problem is no more difficult than solving a commonly used approximation of the problem

the joint economic lot size problem a review abstract this article reviews lot size models which focus on coordinated inventory replenishment decisions between buyer and vendor and their impact on the performance of the supply chain these so called joint economic lot size jels models determine order production and shipment quantities from the perspective of the supply chain with the objective of minimizing total system costs this paper first describes the problem studied introduces the methodology of the review and presents a descriptive analysis of the selected papers subsequently papers are categorized and analyzed with respect to their contribution to the coordination of different echelons in the supply chain finally the review highlights gaps in the existing literature and suggests interesting areas for future research

takeover threats and managerial myopia this paper examines the familiar argument that takeover pressure can be damaging because it leads managers to sacrifice long term interests in order to boost current profits if stockholders are imperfectly informed temporarily low earnings may cause the stock to become undervalued increasing the likelihood of a takeover at an unfavorable price hence the managerial concern with current bottom line the magnitude of the problem depends on a variety of factors including the attitudes and beliefs of shareholders the extent to which corporate raiders have inside information and the degree to which managers are concerned with retaining control of their firms

could good intentions backfire an empirical analysis of the bank deposit insurance the recent financial crisis led to the expansion of deposit insurance coverage in many countries we develop a structural model of the banking market in which banks act as financial intermediaries between consumers who have funds and businesses that seek loans and explore the implications of such policies for banks and depositors our results indicate the policy could erode market discipline and increase banks moral hazard as a result banks extend their lending to riskier loans than they would have in the absence of the policy we find this policy may even harm consumers moreover market competition magnifies the lack of market discipline and induces additional moral hazard for excessive risk taking counterfactuals indicate banks may reduce their deposit interest rates by 2 7 in a duopoly market and almost triple their risk caps under the new policy the estimated losses of depositors welfare are equivalent to at least a 3 27 drop in deposit interest rates data are available at https doi org 1

economic production quantity model for items with imperfect quality abstract the assumptions necessary to justify the use of economic production quantity epq eoq models are rarely met to provide mathematical models that more closely conform to actual inventories and respond to the factors that contribute to inventory costs the models must be extended or altered this paper hypothesizes a production inventory situation where items received or produced are not of perfect quality items of imperfect quality not necessarily defective could be used in another production inventory situation that is less restrictive process and acceptance control the electronics industry gives good examples of such situations this paper extends the traditional epq eoq model by accounting for imperfect quality items when using the epq eoq formulae this paper also considers the issue that poor quality items are sold as a single batch by the end of the 100 screening process a mathematical model is developed and numerical examples are provided to illustrate the solution procedure

analysis of postponement strategy for perishable items by eoq based models abstract this paper develops economic order quantity model eoq based models with perishable items to evaluate the impact of a form postponement strategy on the retailer in a supply chain we formulate models for a postponement system and an independent system to minimize the total average cost function per unit time for ordering and keeping n perishable end products an algorithm is given to derive the optimal solutions of the proposed models the impact of the deterioration rate on the inventory replenishment policies is studied with the help of theoretical analysis and numerical examples our theoretical analysis and computational results show that a postponement strategy for perishable items can give a lower total average cost under certain circumstances

economic order quantity for items with imperfect quality revisited abstract we rectify a flaw in an economic order quantity eoq model with unreliable supply characterized by a random fraction of imperfect quality items and a screening process developed by salameh and jaber 2000 economic production quantity model for items with imperfect quality international journal of production economics 64 1 3 59 64 this leads to simple expressions of the optimal order quantity and expected profit per unit time we then analyze the effect of screening speed and variability of the supply process on the order quantity and show that the order quantity in our model is larger than that of the classical eoq model when the variability of the yield rate is reasonably low in addition we extend the model by allowing for several batches of imperfect quality items to be consolidated and shipped in one lot this is likely to be useful when there are economies of scale in shipping of imperfect quality items finally we present numerical results to illustrate the application of the model and draw insights

economic production quantity model for items with imperfect quality subject to learning effects abstract salameh and jaber 2000 international journal of production economics 64 59 64 developed an inventory situation where items received are not of perfect quality defective and after 100 screening imperfect quality items are withdrawn from inventory and sold at a discounted price this paper extends the work of salameh and jaber by assuming the percentage defective per lot reduces according to a learning curve which was empirically validated by data from the automotive industry mathematical models are developed with numerical examples provided and discussed the developed model was compared with the model of salameh and jaber to emphasize the importance of learning

effects of discounting and demand rate variability on the eoq the economic order quantity eoq formula is probably the most well known formula in inventory theory it determines the optimal value of the ordering quantity by minimizing the average cost in an ordering cycle it is based on the assumptions that there is a fixed lead time and a constant demand rate these assumptions are usually not fulfilled in practice especially when dealing with slow moving items demand seems to fluctuate furthermore since the time between two successive orderings is often large for slow moving items discounted costs instead of average costs should be minimized in this paper we determine the optimal ordering quantity if demand is modelled by a poisson process and the expected discounted costs are minimized we also analyze the case where demand is uniform and or the average cost criterion is used we give graphical presentations of the optimal ordering quantities besides easily determining the optimal values these allow us to show what the effects of changing the objective function and of changing the demand distribution are we derive a simple discounted cost ordering quantity formula denoted by eoq d for slow moving items we show that for items with a small demand rate and high fixed ordering costs the eoq d is much closer to the optimal discounted cost ordering quantity than the traditional eoq formula c 1998 elsevier science b v all rights reserved

incorporating quantity discounts to the eoq model with transportation costs abstract this article extends a previous economic order quantity eoq model with two modes of transportation namely truckload tl and less than truckload ltl carriers by introducing all units and incremental quantity discount structures into the analysis exact algorithms are developed for each quantity discount structure to compute optimal policies for single stage models over an infinite planning horizon

ceo pay firm size and corporate performance evidence from canada executive compensation of 755 canadian firms is examined over the period 1991 95 and evidence is obtained consistent with previous studies ceo pay rises with firm size and compensation is tied to company performance in addition executives in utilities earn lower pay and their compensation is less responsive to performance than is true for their counterparts in other industries some novel findings are also documented first the sales elasticity of ceo compensation is greater in larger firms second while ceo turnover probability is generally negatively related to the firm s stock performance the threat of dismissal appear to be less pronounced in small firms jel classification g35 j33 salaire des pdg taille de l entreprise et performance des societes resultats pour le canada en etudiant le salaire des pdg de 755 entreprises canadiennes au cours de la periode 1991 95 l auteur confirme certains resultats d etudes anterieures le salaire du pdg croit avec la taille de l entreprise et il est liea la performance de l entreprise il appert aussi que les cadres dans les entreprises de service public gagnent moins relativement parlant et que leur salaire est moins sensible aux ecarts de performance que dans les autres secteurs on met aussi a jour certains resultats inedits d abord il semble que l elasticite du salaire du pdg par rapport au niveau des ventes est plus forte dans les plus grandes entreprises ensuite alors que la probabilite de roulement est en general co reliee negativement a la performance des actions en bourse de l entreprise la menace de renvoi semble moins prononcee dans les petites entreprises

does tax policy affect executive compensation evidence from postwar tax reforms abstract the trends in executive pay and labor income tax rates since the 1940s suggest a high elasticity of taxable income with respect to tax policy by contrast the level and structure of executive compensation have been largely unresponsive to tax incentives since the 1980s however the relative tax advantage of different forms of pay was small during this period using a sample of top executives in large firms from 1946 to 2005 we also find a small short run response of salaries qualified stock options and bonuses paid after retirement to changes in tax rates on labor income even though tax rates were significantly higher and more heterogeneous across individuals in the first several decades following wwii we explore several potential explanations for the conflicting impressions given by the long run and short run correlations between taxes and pay including changes in social norms and concerns about pay equality

economic ordering quantity models for items with imperfect quality abstract in this paper we first look at the issue of non shortages in models with proportional imperfect quality when the proportion of the imperfects is a random variable more specifically we revisit the papers of salameh and jaber int j prod econom 64 2000 59 and chan et al prod plann control 14 2003 588 and we point out that the sufficient conditions given in these papers to ensure that shortages will not occur may not really prevent their occurrence next considering the timing of withdrawing the imperfect quality items from stock we clarify a point not clearly stated in salameh and jaber int j prod econom 64 2000 59 and we extented this model to the case in which withdrawing takes place at the end of the planning horizon finally we establish that the objective of maximizing the mean average profit which was set in salameh and jaber int j prod econom 64 2000 59 is superfluous and the results given there can be obtained by ignoring the revenue issues assumed in the model and minimizing directly the mean average cost

does deposit insurance improve financial intermediation evidence from the russian experiment this study examines how the introduction of deposit insurance affects depositors and banks using the deposit insurance scheme introduced into the russian banking system as a natural experiment the fundamental research question is whether the introduction of deposit insurance leads to a more effective banking system as evidenced by increased deposit taking and decreased reliance upon state owned banks as custodians of retail deposits we find that banks entering the new deposit insurance system increase both their level of retail deposits and their ratios of retail deposits to total assets relative to banks that do not enter the new deposit insurance system these results hold up in a multivariate panel data analysis that controls for bank and time random effects the longer a bank has been entered into the deposit insurance system the greater is its level of deposits and its ratio of deposits to assets moreover this effect is stronger for regional banks and for smaller banks we also find that implementation of the new deposit insurance system has the effect of leveling the playing field between state owned banks and privately owned banks finally we find strong evidence of moral hazard following implementation of deposit insurance in the form of increased bank risk taking financial risk and to a lesser degree operating risk increase following implementation

the elasticity of taxable income evidence and implications abstract a central tax policy parameter that has recently received much attention but about which there is substantial uncertainty is the overall elasticity of taxable income we provide new estimates of this elasticity which address identification problems with previous work by exploiting a long panel of tax returns to study a series of tax reforms throughout the 1980s this identification strategy also allows us to provide new evidence on both the income effects of tax changes on taxable income and on variation in the elasticity of taxable income by income group we find that the overall elasticity of taxable income is approximately 0 4 the elasticity of real income not including tax preferences is much lower we estimate small income effects of tax changes on reported income implying that the compensated and uncompensated elasticities of taxable income are very similar we estimate that this overall elasticity is primarily due to a very elastic response of taxable income for taxpayers who have incomes above 100 000 per year who have an elasticity of 0 57 while for those with incomes below 100 000 per year the elasticity is less than one third as large moreover high income taxpayers who itemize are particularly responsive to taxation our estimates suggest that optimal tax structures may feature tightly targeted transfers to lower income taxpayers and a flat or even declining marginal rate structure for middle and high income taxpayers

closed form solutions for wee s and martin s eoq models with a temporary price discount abstract in this article we use closed form solutions to solve wee and yu 1997 deteriorating inventory model with a temporary price discount and martin s 1994 eoq model with a temporary sale price in wee and yu 1997 and martin s 1994 the benefits during the temporary price discount purchase cycle are represented by their objective functions wee and yu 1997 and martin 1994 only used search methods to find approximate solutions following the theorems we suggested you can find closed form solution directly when there are integer operators involve in an objective function using the data of wee and yu 1997 and martin 1994 we can find the results are more quick and more accurate

economic order quantity model for items with imperfect quality with learning in inspection abstract the economic order quantity eoq model is the simplest and earliest inventory model in the literature its simple mathematics is attributed to its assumptions which are rarely met salameh and jaber 2000 economic production quantity model for items with imperfect quality int j prod econ 64 59 64 addressed one of these assumptions that items received or produced are not of perfect quality this paper extends salameh and jaber s work for the case where there is learning in inspection the model is realistic in that it considers situations of lost sales and backorders mathematical models are developed with numerical examples provided and results discussed for the cases of i partial transfer of learning ii total transfer of learning and iii no transfer of learning

an economic order quantity model for deteriorating items with partially permissible delay in payments linked to order quantity abstract to attract more sales suppliers frequently offer a permissible delay in payments if the retailer orders more than or equal to a predetermined quantity w in this paper we generalize goyal s k 1985 eoq under conditions of permissible delay in payments journal of the operational research society 36 335 338 economic order quantity eoq model with permissible delay in payment to reflect the following real world situations 1 the retailer s selling price per unit is significantly higher than unit purchase price 2 the interest rate charged by a bank is not necessarily higher than the retailer s investment return rate 3 many items such as fruits and vegetables deteriorate continuously and 4 the supplier may offer a partial permissible delay in payments even if the order quantity is less than w we then establish the proper mathematical model and derive several theoretical results to determine the optimal solution under various situations and use two approaches to solve this complex inventory problem finally a numerical example is given to illustrate the theoretical results