a fuzzy vendor managed inventory of multi item economic order quantity model under shortage an ant colony optimization algorithm abstract in this study a multi item economic order quantity model with shortage under vendor managed inventory policy in a single vendor single buyer supply chain is developed this model explicitly includes warehouse capacity and delivery constraints bounds order quantity and limits the number of pallets not only the demands are considered imprecise but also resources such as available storage and total order quantity of all items can be vaguely defined in different ways an ant colony optimization is employed to find a near optimum solution of the fuzzy nonlinear integer programming problem with the objective of minimizing the total cost of the supply chain since no benchmark is available in the literature a genetic algorithm and a differential evolution are developed as well to validate the result obtained furthermore the applicability of the proposed methodology along with a sensitivity analysis on its parameter is demonstrated using five numerical examples containing different numbers of items

living arrangements doubling up and the great recession was this time different abstract the great recession marks the worst downturn since those of the early 1980s a large literature considers how the public safety net responded to this shock we instead consider the responsiveness of one dimension of the private safety net families can react to negative shocks by moving in with relatives or downsizing we use across state over time variation to estimate the effects of cycles on living arrangements paying particular attention to young adults we find living arrangements are cyclical but effects are small surprisingly given the press attention we find no evidence that things are different in the great recession

booms busts and babies health we study the relationship between the unemployment rate at the time of a baby s conception and parental characteristics parental behaviors and babies health babies conceived in times of high unemployment have a reduced incidence of low and very low birth weight fewer congenital malformations and lower post neonatal mortality these health improvements are attributable both to selection changes in the type of mothers that conceive during recessions and to improvements in health behavior during recessions black mothers tend to be higher socio economic status as measured by education and marital status in times of high unemployment whereas white mothers are less educated

language and the earnings of immigrants several studies most of them employing straightforward regression analysis have concluded that immigrants proficiency in the language of their adopted country is correlated with their productivity as measured by earnings two weaknesses of these studies are potential unobserved heterogeneity which could result in over estimated effects if overall ability is linked with language acquisition and potential measurement error in the language proficiency measures which would probably result in under estimation of language effects the present study which uses panel data for a 10 year period in germany yields evidence that the latter bias tends to be much larger than the former implying that language proficiency is far more important than suggested by the existing literature

accounting for the decline in afdc caseloads welfare reform or the economy we use state level monthly panel data to assess the relative contributions of the macroeconomy and welfare reform in accounting for the 1993 96 decline in aid to families with dependent children afdc caseloads our results suggest that the decline in per capita afdc caseloads is attributable largely to the economic conditions in states and not to waivers from federal welfare policies nationwide we attribute 66 percent of the decline to the macroeconomy however we do find substantial heterogeneity in the impact and timing of alternative waivers on afdc caseloads states with waivers impacting parental responsibilities experienced greater caseload declines than states with waivers that made work more attractive overall our model predicts that had it not been for the influence of economic factors welfare reform would not have led to any decrease in aggregate caseloads

a generalized quantity discount pricing model to increase supplier s profits in this paper the joint problem of ordering and offering price discount by a supplier to his sole major buyer is analyzed the objective is to induce the buyer to alter his order schedule and size so that the supplier can benefit from lower set up ordering and inventory holding costs we generalize the quantity discount pricing model of monahan monahan j p 1984 a quantity discount pricing model to increase vendor profits management sci 30 6 720 726 to 1 explicitly incorporate constraints imposed on the amount of discount that can be offered and 2 relax the implicit assumption of a lot for lot or order for order policy adopted by the supplier an algorithm is developed to solve the supplier s joint ordering and price discount problem

a heuristic for single warehouse multiretailer supply chains with all unit transportation cost discounts abstract in supply chain management research transportation costs if explicitly considered at all are frequently assumed to be linear these costs often have a more complex form such as an all unit discount structure this piecewise cost function adds significant complexity when included in supply chain management problems and is therefore often ignored due to solution time or tractability concerns we present and evaluate a new heuristic procedure which provides good solutions to problems involving all unit discount cost functions while significantly reducing solution times the general nature of this procedure does not require assumptions about the supply chain structure or policies and is therefore applicable in a wide range of settings

a hybrid algorithm for simultaneous scheduling of production and distribution in multi echelon structures this paper presents a dynamic programming algorithm for simultaneous determination of production batch sizes in an assembly network and distribution batch sizes in a conjoined distribution arborescent network the objective is to minimize average cost per period over an infinite horizon costs consist of processing costs at each node and linear holding costs for inventory final product demand rates may vary among the retail nodes but at each retail node the demand rate is assumed to be known constant and continuous all demand must be met backorders are not permitted the model can be used for a single product or for several products that are temporarily combined for distribution or for scheduling production in a system where several end products are produced from the same intermediate product as in some biochemical manufacturing processes

parametric analysis of setup cost in the economic lot sizing model without speculative motives in this paper we consider the important special case of the economic lot sizing problem in which there are no speculative motives to hold inventory we analyze the effects of varying all setup costs by the same amount this is equivalent to studying the set of optimal production periods when the number of such periods changes we show that this optimal set changes in a very structured way this fact is interesting in itself and can be used to develop faster algorithms for such problems as the computation of the stability region and the determination of all efficient solutions of a lot sizing problem furthermore we generalize two related convexity results which have appeared in the literature

long term and penalty contracts in a two stage supply chain with stochastic demand abstract recent applications of game theoretic analysis to supply chain efficiency have focused on constructs between a buyer the retailer or manufacturer and a seller the supplier in successive stages of a supply chain if demand for the final product is stochastic then the supplier has an incentive to keep its capacity relatively low to avoid creating unneeded capacity the manufacturer on the other hand prefers the supplier s capacity to be high to ensure that the final demand is satisfied the manufacturer therefore constructs a contract to induce the supplier to increase its production capacity most research examines contracting when final demand is realized after the manufacturer places its order to the supplier however if final demand is realized before the manufacturer places its order to the supplier these types of contracts can be ineffective this paper examines two contracts under the latter timing scenario long term contracts in which the business relationship is repeated and penalty contracts in which the supplier is penalized for too little capacity results indicate long term contracts increase the profit potential of the supply chain furthermore the penalty contracts can ensure that the supplier chooses a capacity level such that the full profit potential is achieved

optimal stationary policies in a 3 stage serial production distribution logistic chain facing constant and continuous demand in this paper we study a 3 stage production distribution system that faces constant and continuous demand the system is made up of three storing sites a production facility a warehouse and a retailer this system was constructed to study the need for coordinating distribution and production in the decision of lot sizes hence the production capacity is limited our objective is to compute lot sizes that leads to the lowest possible cost in such a system we consider stationary inventory management policies in such a policy a fixed lot size is supplied from one stage to the next with a constant time interval we introduce the concept of multiple policies and give a solution to find the best one we then prove that multiple policies are guaranteed to cost less than 1 51 more than the best stationary policy we improve this guarantee to 0 51 by adding some simple but non multiple policies to our candidate policies

food stamp caseloads over the business cycle 1 introduction the onset of the current economic downturn following the longest expansion in u s history has renewed interest in the role of automatic stabilizers designed to insure households against negative cyclical income shocks this system of income and consumption stabilizers includes among others the individual income tax and the panoply of social insurance programs such as unemployment insurance and the food stamp program while the income tax and unemployment insurance have received recent attention gruber 1997 auerbach and feenberg 2000 kniesner and ziliak 2002a b little is known about the role of food stamps as an automatic stabilizer even though the program served over 27 million americans at its peak in 1994 this gap in the literature is particularly acute in light of passage of the personal responsibility and work opportunity reconciliation act of 1996 welfare reform act which introduced new rules on cash assistance recipients and thus the nearly half of food stamp recipients who also receive cash welfare moreover the 1996 welfare reform also had a direct administrative effect on the food stamp program by ending the eligibility of some recipients reducing average benefit levels and requiring states to replace paper coupons with electronic benefit transfer cards importantly the welfare reform act also eliminated the entitlement status of the main cash welfare program aid to families with dependent children afdc thus positioning food stamps as a more prominent countercyclical consumption stabilizer a first task in assessing the possible stabilization role of food stamps in the era of welfare reform is to identify the cyclical sensitivity of food stamp caseloads if food stamp caseloads are acyclical then we would expect no role for food stamps in smoothing consumption over the business cycle if however food stamp caseloads are highly cyclical then food stamps may function as an important antirecessionary tool by the same token the new welfare policies may independently affect food stamp caseload movements and interact with the business cycle thereby altering the possible stabilization role of the program in this paper we specify a dynamic model of food stamp caseloads to estimate the responsiveness of the caseload to the business cycle to welfare policies and to interactions between the business cycle and welfare policies unlike cash welfare there has been scant research on the cyclicality of food stamp caseloads 1 wallace and blank 1999 are a recent exception in their use of both static annual and dynamic monthly food stamp caseload models based on state level panel data for the 1980 to 1998 federal fiscal years with annual data food stamp caseloads were strongly countercyclical and reform of afdc led to weak declines in total caseloads 2 specifically they attribute up to 44 of the 1994 to 1998 food stamp caseload decline to economic conditions and about 6 of the decline to welfare reform they reach broadly similar conclusions with monthly data however wallace and blank calculate that upward of 85 of the post 1996 decline in food stamp caseloads can be attributed to welfare reform if one is willing to ascribe all the unexplained residual to welfare reform which as the authors note is undoubtedly an overestimate of welfare reform s effect on food stamp caseloads p 85 in their static models figlio gundersen and ziliak 2000 reached conclusions similar to wallace and blank s estimates with annual level data in their preferred dynamic models they attribute about 35 of the 1994 to 1998 caseload decline to the macroeconomy and virtually nothing to welfare reform we improve on this previous research on food stamp caseloads along several dimensions first we not only follow other research in estimating the impact of afdc policy changes on food stamp caseloads but also examine the impact of policies that are focused directly on food stamps

disaggregating the effect of the business cycle on the distribution of income this paper disaggregates total household income into a complete set of components and studies the comparative cyclicality of these com ponent to economic growth comparisons of the relative responsiveness to gnp growth of wages hours of work and total labor market income of heads and wives and transfer income sources of households are made across income race sex and age groups this provides a picture of the channels by which economic growth produces income change significant differences in elasticities are found to exist both between different income components and between different population groups for the same component the narrowing income distribution in times of high growth occurs primarily because of large elasticities on head s labor market income among the poor both wages and hours show evidence of cycli cality the labor market earnings of women both wives and household heads is far less responsive to growth cyclicality in transfer income varies enormously between population groups and by type of transfer

coordinating a three level supply chain with learning based continuous improvement abstract learning curve theory has been widely used as a managerial tool to describe and model product and process improvement this paper investigates a three level supply chain supplier manufacturer retailer where the manufacturing operations undergo a learning based continuous improvement process improvements in the manufacturer s operation are characterized by enhanced capacity utilization reductions in set ups times and improved product quality through the elimination of rework as a result of these continuous improvements the manufacturer can justify a production policy that is based on more frequent smaller lot size production for this production policy to be practical and not sub optimal to the supply chain the manufacturer must integrate its lot sizing models with the replenishment policies of its upstream raw material suppliers and the demand requirements of its downstream customers retailers mathematical models that achieve chain wide lot sizing integration are developed and solution procedures for the models are illustrated by numerical examples the results demonstrate that learning based improvements in set up time and rework allow retailers to order in progressively smaller lot sizes as the manufacturer offers larger discounts and profits and that the entire supply chain benefits from implementing learning based continuous quality improvements the results also demonstrate that forgetting effects lead to increases in supply chain costs

a stochastic aggregate production planning model in a green supply chain considering flexible lead times nonlinear purchase and shortage cost functions in this paper we develop a stochastic programming approach to solve a multi period multi product multi site aggregate production planning problem in a green supply chain for a medium term planning horizon under the assumption of demand uncertainty the proposed model has the following features i the majority of supply chain cost parameters are considered ii quantity discounts to encourage the producer to order more from the suppliers in one period instead of splitting the order into periodical small quantities are considered iii the interrelationship between lead time and transportation cost is considered as well as that between lead time and greenhouse gas emission level iv demand uncertainty is assumed to follow a pre specified distribution function v shortages are penalized by a general multiple breakpoint function to persuade producers to reduce backorders as much as possible vi some indicators of a green supply chain such as greenhouse gas emissions and waste management are also incorporated into the model the proposed model is first a nonlinear mixed integer programming which is converted into a linear one by applying some theoretical and numerical techniques due to the convexity of the model the local solution obtained from linear programming solvers is also the global solution finally a numerical example is presented to demonstrate the validity of the proposed model

a bargaining model with asymmetric information for a single supplier single buyer problem abstract banerjee s joint economic lot size jels model represents one approach to minimizing the joint total relevant cost of a buyer and a supplier by using a joint optimal order and production policy the implementation of a jointly optimal policy requires coordination and cooperation should the buyer have the market power to implement his own optimal policy as that one to be used in the exchange process no incentive exists for him to choose a joint optimal policy a joint policy can therefore only be the result of a bargaining process between the parties involved the supplier may make some sort of concession such as a price discount or a side payment in order to influence the buyer s order policy a critical assumption made throughout in supply chain literature is that the supplier has complete knowledge about the buyer s cost structure clearly this assumption will seldom be fulfilled in practice the research presented in this paper provides a bargaining model with asymmetric information about the buyer s cost structure assuming that the buyer has the power to impose its individual optimal policy

booms busts and fertility testing the becker model using gender specific labor demand in this paper i present estimates of the effect of local labor demand shocks on birth rates to identify exogenous variation in male and female labor demand i create indices that exploit cross sectional variation in industry composition changes in gender education composition within industries and growth in national industry employment consistent with economic theory i find that improvements in men s labor market conditions are associated with increases in fertility while improvements in women s labor market conditions have smaller negative effects i separately find that increases in unemployment rates are associated with small decreases in birth rates at the state level

an enhanced robustness approach for managing supply and demand uncertainties abstract managing supply and demand uncertainties is a topic that receives increasing management attention due to 1 more price based competitions forcing firms purchase from cheaper but less reliable or unproven suppliers and 2 undesirable consequences of unaddressed demand fluctuations such as reduced service level financial loss reputational damage and loss of market share this paper presents a realistic production distribution planning model that is robust to common supply interruptions and demand variations a robustness approach named elastic p robustness is introduced that obviates the need to estimate probability distribution of random parameters when managing operational uncertainties of the supply chain the application of the proposed approach is investigated in an actual organization from discrete durable parts manufacturing sector our analyses of numerical results focus on 1 exploring different tactics for managing supply and demand variations 2 examining the benefits of concurrent consideration of supply and demand uncertainties 3 benchmarking the performance of the proposed approach against the popular robustness algorithms and 4 investigating the price of robustness under various supply and demand scenarios

determining profit maximizing production shipping policies in a one to one direct shipping stochastic demand environment abstract in this paper we consider the problem of producing and transporting a unique product directly from an origin e g a production plant to a destination e g its retail outlet where demands are stochastic and follow a known probability distribution we first derive the expected profit per unit produced and shipped as a function of the production rate and shipment size for a general demand distribution then an iterative procedure is designed to obtain the optimal production shipping policies by exploiting the concavity of the expected profit function on the production rate for the uniform demand distribution case monte carlo experiments and sensitivity analyses are also performed to validate the model and give further insights into the effect of changes in parameter values on the optimal policies and the expected profit function this research extends the classic newsboy model by combining the production and logistical decisions into an integrated framework and provides optimal production shipping policies for profit oriented organizations that own both the production and retail entities and face demand uncertainties

heterogeneity in the impact of economic cycles and the great recession effects within and across the income distribution abstract in this paper we examine the effects of economic cycles on low to moderate income families we use variation across states and over time to estimate the effects of cycles on the distribution of income using fine gradations of the household income to poverty ratio we also explore how the effects of cycles affect the risk of falling into poverty across demographic groups focusing on age race ethnicity and family type we conclude by testing to see whether these relationships have changed in the great recession we discuss the results in light of the changes in the social safety net in recent decades

immigrant language fluency in the low skilled labor market using longitudinal linked employer employee data the author investigates the returns to being a native speaker for immigrant men in the low skilled labor market she compares the two main recent immigrant groups in portugal brazilians who are portuguese native speakers and eastern europeans who are not findings show that both wage level and wage growth of the two groups are similar to better understand this surprising result the author studies two mechanisms through which language fluency may lead to higher wages sorting across occupations and across firms brazilians do sort into occupations that require greater language skills however this does not translate into a wage premium considerable workplace segregation occurs in portugal but brazilians are not less segregated from natives than are eastern europeans evidence in this article suggests that language skills are not a major driver of economic assimilation in the low skilled labor market

the impact of cost uncertainty on the location of a distribution center abstract the location of a distribution center dc is a key consideration for the design of supply chain networks when deciding on it firms usually allow for transportation costs but not supplier prices we consider simultaneously the location of a dc and the choice of suppliers offering different possibly random prices for a single product a buying firm attempts to minimize the sum of the price charged by a chosen supplier and inbound and outbound transportation costs no costs are incurred for switching suppliers we first derive a closed form optimal location for the case of a demand populated unit line between two suppliers offering deterministic prices we then let one of the two suppliers offer a random price if the price follows a symmetric and unimodal distribution the optimal location is closer to the supplier with a lower mean price we also show the dominance of high variability the buyer can decrease the total cost more for higher price variability for any location the dominance result holds for normal uniform and gamma distributions we propose an extended model with more than two suppliers on a plane and show that the dominance result still holds from numerical examples for a line and a plane we observe that an optimal location gets closer to the center of gravity of demands as the variability of any supplier s price increases

the performance of immigrants in the canadian labor market in this article we examine the economic assimilation of immigrants to canada we provide new evidence on immigrants who arrived in the 1970s and document an increase in the dispersion of labor market outcomes across immigrants of different vintages over time our results confirm u s evidence of permanent differences across immigrant cohorts what distinguishes the canadian experience is small or negative rates of assimilation for most cohorts over the sample period finally we test the overidentification of the assimilation process specified in previous studies and fail to reject the usual cohort fixed effect specification

an integrated inventory model for a single vendor and multiple buyers with ordering cost reduction abstract forming strategic alliances and utilizing modern information technologies have been the two most important ways for firms to gain such competitive advantages as lower logistics costs and secure customers loyalty in this paper we consider an integrated inventory system where a single vendor purchases and processes raw materials in order to deliver finished items to multiple buyers the vendor and all buyers are willing to invest in reducing the ordering cost e g establishing an electronic data interchange based inventory control system in order to decrease their joint total cost the amount of investment determines the planned ordering cost and hence affects their replenishment decisions one major managerial implication from this ordering cost reduction is that the efforts to streamline and speedup transactions via the application of information technologies may result in a higher degree of coordination and automation among allied trading parties an analytical model is developed to derive the optimal investment amount and replenishment decisions for both vendor and buyers the exponential ordering cost function is then applied to our general model and a numerical analysis is performed to provide interesting insights of the model numerical results show that the vendor and all the buyers can benefit directly from substantial cost savings by this ordering cost reduction investment

diversification under supply uncertainty supply chain management is becoming an increasingly important issue especially when in most industries the cost of materials purchased comprises 40 60 of the total sales revenue despite the benefits cited for single sourcing in the popular literature there is enough evidence of industries having two three sources for most parts in this paper we address the operational issue of quantity allocation between two uncertain suppliers and its effects on the inventory policies of the buyer based on the type of delivery contract a buyer has with the suppliers we suggest three models for the supply process model i is a one delivery contract with all of the order quantity delivered either in the current period with probability or in the next period with probability 1 model ii is also a one delivery contract with a random fraction of the order quantity delivered in the current period the portion of the order quantity not delivered is cancelled model iii is similar to model ii with the remaining quantity delivered in the next period we derive the optimal ordering policies that minimize the total ordering holding and penalty costs with backlogging we show that the optimal ordering policy in period n for each of these models is as follows for x a n order nothing for vi n x a n use only one supplier and for x vi n order from both suppliers for the limiting case in the single period version of model i we derive conditions under which one would continue ordering from one or the other or both suppliers for model ii we give sufficient conditions for not using the second more expensive supplier when the demand and yield distributions have some special form for the single period version of models ii and iii with equal marginal ordering costs we show that the optimal order quantities follow a ratio rule when demand is exponential and yields are either normal or gamma distributed

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

education credentials and immigrant earnings using 1981 to 2001 census data we study how the human capital of immigrants is rewarded in canada we distinguish between years of schooling and degrees obtained in order to estimate sheepskin effects the gain in earnings associated with receipt of a degree controlling for years of schooling we find that immigrant years of schooling and immigrant work experience accumulated before arrival is valued much less than canadian experience of comparable natives however for immigrants the increase in earnings associated with completing educational programs is generally higher than that of comparable natives we provide both signalling and human capital interpretations of this finding a l aide des donnees de recensement entre 1981 et 2001 on examine la facon dont le capital humain des immigrants est reconnu et remunere au canada on fait la distinction entre les annees de scolarite et les grades obtenus afin de calibrer les effets du diplome les gains associes a l obtention du grade apres avoir pris en compte les annees de scolarite on decouvre que les annees de scolarite et d experience accumulees par les immigrants avant leur arrivee recoivent une ponderation moins grande que l experience comparable des canadiens cependant pour les immigrants le fait de completer leur programme a un effet sur l accroissement des revenus qui est plus important que pour les canadiens de souche on suggere des interpretations de ces resultats a partir de theorisations fondees sur le capital humain et la theorie des signaux

integrated production distribution planning in supply chains an invited review ss selc suk ereng uc s n c simpson asoo j vakharia c a department of decision and information sciences college of business administration university of florida gainesville fl 32611 7169 usa b department of management science and systems school of management university at bu alo bu alo ny 14260 4000 usa c department of decision and information sciences college of business administration university of florida 343 bus p o box 117169 gainesville fl 32611 7169 usa

using differences in knowledge across neighborhoods to uncover the impacts of the eitc on earnings we develop a new method of estimating the impacts of tax policies that uses areas with little knowledge about the policy s marginal incentives as counterfactuals for behavior in the absence of the policy we apply this method to characterize the impacts of the earned income tax credit eitc on earnings using administrative tax records covering all eitc eligible lers from 19962009 we begin by developing a proxy for local knowledge about the eitc schedule the degree of sharp bunching at the exact income level that maximizes eitc refunds by individuals who report self employment income the degree of self employed sharp bunching varies signi cantly

revisiting foundations in lot sizing connections between harris crowther monahan and clark abstract while many review articles exist on deterministic lot sizing models used in the context of price and quantity discounts buyer vendor coordination supply chain management and joint economic lot sizing problems they do not convey the impact of important findings which date back to at least 2002 or in hindsight to 1984 as a result many recent articles still model the financial implications of lot sizing decisions without having the assurance that these models would help the firm s involved in maximising the net present value npv this paper therefore reviews these findings while adding also its own contributions as to convey the general importance to lot sizing theory we show that the underlying principles used in the four key articles that have led to a division in modelling approaches are in fact all in line with npv and argue that therefore there should not be these discrepancies that currently persist in the literature we establish the connections between these four strands of the literature using the solution to a simple variation of harris eoq model deriving thereby results from boyaci and gallego 2002 and beullens and janssens 2011 but showing their general applicability to any type of supply chain structure the breath of implications to deterministic lot sizing theory is illustrated using practical examples we present a stochastic version of the model of crowther 1964 which is arguably the least understood and applied model but on the other hand the most important one in realising how these modelling strands can be unified

effective policy for reducing poverty and inequality the earned income tax credit and the distribution of income we examine the effect of the eitc on the poverty and income of single mothers with children using a quasi experimental approach that leverages variation in generosity due to policy expansions across tax years and family sizes we find that the income increasing effects of the eitc are concentrated between 75 and 150 percent of income to poverty with little effect at the lowest income levels and at levels of 250 percent of poverty and higher we use these results to show that by failing to capture the indirect effects of the credit on earnings static calculations of the antipoverty effects of the eitc may be underestimated by almost 50 percent abstract from author

integrated lot sizing in serial supply chains with production capacities we consider a model for a serial supply chain in which production inventory and transportation decisions are integrated in the presence of production capacities and concave cost functions the model we study generalizes the uncapacitated serial single item multilevel economic lot sizing model by adding stationary production capacities at the manufacturer level we present algorithms with a running time that is polynomial in the planning horizon when all cost functions are concave in addition we consider different transportation and inventory holding cost structures that yield improved running times inventory holding cost functions that are linear and transportation cost functions that are either linear or are concave with a fixed charge structure in the latter case we make the additional common and reasonable assumption that the variable transportation and inventory costs are such that holding inventories at higher levels in the supply chain is more attractive from a variable cost perspective while the running times of the algorithms are exponential in the number of levels in the supply chain in the general concave cost case the running times are remarkably insensitive to the number of levels for the other two cost structures

integrated production and allocation policies with one direct shipping option we consider a single period inventory problem in which a supplier faces stochastic demands and customer specific waiting costs from multiple customers the objective is to develop integrated production allocation and distribution policies so that the total production and customer waiting costs are minimized we present an optimal policy for the two customer problem and derive a heuristic for a general problem based on the structural results of the two customer case we show numerically that the heuristic performs very well with error bounds of less than 2 on average while typical approximations may lead to significant sub optimality

simulation based sequencing and lot size optimisation for a production and inventory system with multiple items abstract we investigate the following decision problem a manufacturing unit has to meet a random demand for n items at the same time only one item can be manufactured manufacturing times are random whereas set up times are known positive constants but different for different items finished production is stored in a warehouse with finite capacity the availability of raw material is always guaranteed demand that cannot be satisfied by items in the warehouse will be backordered in a queue with given capacity demand that meets a full backorder queue is lost we assume cost for manufacturing items for production switches for holding items in the warehouse for waiting and lost demand for sold items a given reward is earned the problem now is to define such a manufacturing policy i e a sequencing rule and a lot size rule which maximises the expected profit per time unit since that problem is too complex for an analytical solution we restrict our search for an optimal policy to simple structured policies which can be described by a few parameters to find optimal parameter values we use simulation optimisation where a simulator for the system is combined with a genetic algorithm as an optimiser the paper is finished with some numerical examples to show the applicability of the proposed approach

the effects of time limits the eitc and other policy changes on welfare use work and income among female headed families of all of the welfare reforms that were implemented during the 1990s time limits may represent the single greatest break from past policy this paper expands on what is known about this important welfare reform measure by exploiting the predictions from grogger and michalopoulos 2003 to estimate the effects of time limits on welfare use employment labor supply earnings and income among female headed families results based on data from the march current population survey suggest that time limits have had important effects on welfare use and work accounting for about one eighth of the decline in welfare use and about 7 of the rise in employment since 1993 they have had no significant effect on earnings or income however the analysis also shows that the collective effects of other reforms have had important impacts on employment and labor supply furthermore it identifies the earned income tax credit eitc as a particularly important contributor to both the recent decrease in welfare use and t

the myth of immigrant women as secondary workers evidence from canada the existing literature on the employment choices and trajectories of women in immigrant families is divided some researchers argue that immigrant women are secondary workers that is they join the labor market mostly as a response to family income shocks and become employed mainly in unskilled jobs to support their husbands investment in local skills long 1980 baker and benjamin 1997 worswick 1999 as men assimilate and financial constraints ease their spouses participation in the labor market is expected to drop to levels similar to those of native born women this view is however at odds with findings in blau et al 2003 among others where married immigrant women make labor supply decisions guided by their own opportunities in the labor market as natives do rather than conditional on the needs of their partners blau and khan 2007 1 to determine the patterns of labor participation and earnings of female immigrants in this paper we exploit a sample of over 800 000 women taken from the canadian census for the period from 1991 to 2006 combining it with information on the skill requirements of the jobs women hold besides employing a large data set this paper is the first one to assess the labor market advancement of immigrant women through the changes in the task content of their occupations in line with recent work in the labor field acemoglu and autor 2011 our findings reveal that labor behavior of female immigrants in canada seems to follow a path of assimilation similar to that of men and that at best only relatively uneducated immigrant women in jobs requiring very basic skills may fit the profile of secondary workers as in kim and varasani 2011 more specifically we find first that the participation rate of immigrant women at arrival is much lower than that of similar natives but that it rises steadily over time second immigrant women participate in unskilled occupations at a much higher rate than canadian women do at first glance this seems consistent with the view that immigrant women are secondary workers however immigrant women in low skill occupations have a significantly higher level of education than canadian women in the same occupations third the patterns of skill assimilation of educated immigrant women indicate their increasing integration into the labor force over time a reduction in the need for physical strength and a gradual increase in the relative amount of analytical skills required in their jobs

adapting the newsvendor model for infinite horizon inventory systems abstract we address inventory decisions in the context of the reorder point order quantity policy in infinite horizon stochastic lead time demand inventory systems in which the parameters may be non stationary we develop a heuristic policy based on the simple economic order quantity eoq model and the one period newsvendor model using illustrative numerical examples we demonstrate that our simple and easy to understand heuristic policy performs nearly as well as the optimal policy derived from complicated mathematical procedures our heuristic policy is simple easy to implement and flexible in that it can be easily adapted to situations when the parameters of the inventory system may change analytical modeling under non stationary parameters would be extremely complex and the derivation of closed form optimal policies is mathematically intractable in most cases in such cases practitioners will find our heuristic policy an attractive option

the single product lot sizing problem with constant parameters and backlogging exact results a new solution and all parameter stability regions we consider the single product lot sizing problem over a finite planning horizon demand at each period is constant and excess demand is completely backlogged holding and backlogging costs are proportional to the amount of inventory stocked or backlogged while ordering cost is fixed independent of the quantity ordered the optimal policy targets to minimize the total relevant costs over the planning horizon the key results of this paper are 1 an explicit formula for the optimal total cost as a function of the model parameters and the number of cycles of the policy 2 a new polynomial time algorithm which determines the overall optimal policy and 3 stability regions for any solution considering simultaneous variations on all cost and demand parameters the proposed algorithm is easy to implement and therefore is suitable for practical use

who suffers during recessions in this paper we examine how business cycles affect labor market outcomes in the united states we conduct a detailed analysis of how cycles affect outcomes differentially across persons of differing age education race and gender and we compare the cyclical sensitivity during the great recession to that in the early 1980s recession we present raw tabulations and estimate a state panel data model that leverages variation across u s states in the timing and severity of business cycles we find that the impacts of the great recession are not uniform across demographic groups and have been felt most strongly for men black and hispanic workers youth and low education workers these dramatic differences in the cyclicality across demographic groups are remarkably stable across three decades of time and throughout recessionary periods and expansionary periods for the 2007 recession these differences are largely explained by differences in exposure to cycles across industry occupation employment

taxes and the labor market participation of married couples the earned income tax credit a distinguishing feature of recent changes to the us system of public assistance is its increasing focus on working families and reliance on the tax system to transfer dollars to needy families after a decade in near total obscurity the earned income tax credit eitc was expanded to become the largest cash transfer program for lower income families with children advocates of the eitc argue that unlike traditional welfare the credit helps promote both the values of family and work indeed empirical evidence consistent with economic theory suggests that the eitc promotes employment among eligible unmarried women with children to target benefits to lower income families however the eitc is based on family income leading to traditional welfare type disincentives for most eligible secondary earners in fact the eitc is likely to reduce overall family labor supply among married couples this paper examines the labor force participation response of married couples to eitc expansions between 1984 and 1996 the effect of the credit is estimated using both quasiexperimental and traditional reduced form labor supply models results from both models show the same qualitative conclusion that the eitc expansions reduced total family labor supply of married couples in all cases we find a decline in labor force participation by married women that more than offsets any rise in participation by their spouses while the labor force participation rate of married men increased by about 0 2 percentage points that of married women decreased by just over a full percentage point these aggregate effects mask substantial heterogeneity in the population women facing the strongest disincentives were more than 2 percentage points less likely to work after the expansions these findings imply that the eitc is effectively subsidizing married mothers to stay home and therefore have implications for the design of the program d 2003 elsevier b v all rights reserved

english deficiency and the native immigrant wage gap using the interaction of language of country of birth and age at arrival as instruments we find strong evidence of a causal effect of english as additional language eal on the native immigrant wage gap for male employees in the uk

simultaneous determination of multiproduct batch and full truckload shipment schedules abstract a fundamental premise of the well known economic lot scheduling problem elsp is that the finished products are consumed at continuous rates i e their respective cycle inventories are depleted on the basis of unit transactions in today s supply chains however employing complex distribution networks finished goods inventories from manufacturing plants are usually shipped in bulk to succeeding stages along the distribution process moreover existing transport economies often tend to favor full truckload tl rather that partial or less than truckload ltl shipments for economical movement of such goods the scenario examined here however involves a set of products for which individual tl shipments are uneconomical as a remedy we construct a model for taking advantage of tl rates by combining ltl quantities of the items into a full load we adopt the common cycle approach for the elsp in conjunction with a common replenishment cycle as a coordination mechanism that is simple to analyze and implement this is integrated with a periodic full truckload shipping schedule such effective coordination of production and shipment schedules is likely to result in a more streamlined supply chain the concepts developed are illustrated through a simple numerical example

sourcing decisions with capacity reservation contracts abstract by committing to long term supply contracts buyers seek to lower their purchasing costs and have products delivered without interruption when a long term contract is available suppliers are less pressured to find new customers and can afford to charge a price lower than the prevailing spot market price we examine sourcing decisions of a firm in the presence of a capacity reservation contract that this firm makes with its long term supplier in addition to the spot market alternative this contract entails delivery of any desired portion of a reserved fixed capacity in exchange for a guaranteed payment by the buyer we investigate rational actions of the two parties under two different types of periodic review inventory control policies used by the buyer the two number policy and the base stock policy when typical demand probability distributions are considered inclusion of the spot market source in the buyer s procurement plan significantly reduces the capacity commitments from the long term supplier

coordinated supply chain management abstract historically the three fundamental stages of the supply chain procurement production and distribution have been managed independently buffered by large inventories increasing competitive pressures and market globalization are forcing firms to develop supply chains that can quickly respond to customer needs to remain competitive these firms must reduce operating costs while continuously improving customer service with recent advances in communications and information technology as well as a rapidly growing array of logistics options firms have an opportunity to reduce operating costs by coordinating the planning of these stages in this paper we review the literature addressing coordinated planning between two or more stages of the supply chain placing particular emphasis on models that would lend themselves to a total supply chain model finally we suggest directions for future research

multi item inventory systems with joint ordering and transportation decisions abstract in many practical situations joint determination of ordering and transportation decisions for a family of items may lead to a considerable cost saving in this paper we consider a multi item inventory system with a freight rate schedule that is a function of the volume shipped and the capacity of a standard container orders for the family of items are all triggered by a coordinated periodic r s policy economies of scale exist because of the reduced freight rates when ordering a full container load instead of a less than container load a full container load can be achieved by enlarging the initial order quantities a heuristic is proposed to decide whether an initial order should be enlarged or not the heuristic is based on a comparison of the expected saved shipping cost the expected saved ordering cost and the expected extra holding cost caused by an enlargement some numerical examples show that the heuristic works quite satisfactorily

what causes public assistance caseloads to grow this paper uses state panel data to investigate changes in public assistance caseloads through the end of the afdc program in 1996 with particular attention to the rapid increase in caseloads between 1990 and 1994 previous research has focused on total caseloads with attention to economic and policy variables and does a relatively poor job of explaining this caseload increase this paper utilizes a much richer set of control variables to investigate the causes of caseload change it separates afdc caseloads into three subcomponent programs separately investigating changes within the afdc up program afdc child only cases and the remaining core afdc cases with benefits paid to single mothers and their children and it explores whether this caseload rise was driven by changes in takeup rates versus in eligibility the results indicate a large unexplained rise in total afdc caseloads even with a very rich specification a good share of this is due to sharp increases in child only cases driven by program and demographic shifts to a lesser extent this rise was caused by the expansion of afdc up to all states these two factors explain half of the overall rise and all of the unexplained rise in afdc caseloads the remaining increase in core afdc cases benefits received by single mothers and their children is well explained within the model and is the result of economic demographic political and policy changes these variables appear to have increased eligibility among the core afdc population in the early 1990s during the economic slowdown takeup rates also increased during this time period but not by a large amount

non cooperative strategies for production and shipment lot sizing in one vendor multi buyer system abstract this paper considers a decentralized dynamic production distribution control a discrete deterministic model in which a vendor produces a product and supplies it to the buyer is considered several papers on vendor buyer integrated production inventory management assume that policies are set by a central decision maker to optimize total system performance although vendor and buyer may agree to minimize the total cost at least one of them has a private incentive to deviate from the agreement in the competitive situation the objective is to determine schedules which minimize the individual average total cost of production shipment and stockholding we assume that the division of shipment costs is centrally coordinated or negotiated initially it leads to a class of non cooperative constrained games indexed by two parameters connected with partitions of shipment costs non cooperative strategies are considered as feasible strategies in a restricted non cooperative game some properties of equilibrium strategies are investigated as acceptable equilibrium strategies of subgames in the game

assimilation changes in cohort quality and the earnings of immigrants this paper reexamines the empirical basis for two facts that seem to be found in most cross section studies of immigrant earnings 1 the earnings of immigrants grow rapidly as they assimilate into the united states and 2 this rapid growth leads to many immigrants overtaking the earnings of the natives within 10 15 years after immigration using the 1970 and 1980 u s censuses this paper studies the earnings growth experienced by specific immigrant cohorts during the period 1970 80 it is found that within cohort growth is significantly smaller than the growth predicted by cross section regressions for most immigrant groups this differential is consistent with the hypothesis that there has been a secular decline in the quality of immigrants admitted to the united states

in the right place at the wrong time the role of firms and luck in young workers careers we examine administrative data on young german workers and their employers to study the long term effects of an early career job loss to account for nonrandom sorting of workers into firms with different turnover rates and for selective job mobility we use changes over time in firm and age specific labor demand as an instrument for displacement we find that wage losses of young job losers are initially 15 percent but drop to zero within five years only workers leaving very large establishments suffer persistent losses a comparison of estimators implies that initial sorting negative selection and voluntary job mobility biases ordinary least squares estimates toward finding permanent negative effects of early displacements

the significance of federal taxes as automatic stabilizers using the taxsim model for the period 1962 95 we consider the federal tax system s impact as an automatic stabilizer despite the many changes in the tax system there has been relatively little change in its role as an automatic stabilizer we estimate that individual federal taxes offset perhaps as much as 8 percent of initial shocks to gdp we also suggest that the progressive income tax may help to stabilize output via its effect on the supply of labor an additional effect that may even be of similar magnitude to the more traditional path of stabilization through aggregate demand

you can t take it with you immigrant assimilation and the portability of human capital the national origin of an individual s human capital is a crucial determinant of its value education and labor market experience acquired abroad are significantly less valued than human capital obtained domestically this difference can fully explain the earnings disadvantage of immigrants relative to comparable natives in israel variation in the return to foreign schooling across origin countries may reflect differences in its quality and compatibility with the host labor market the return to foreign experience is generally insignificant acquiring additional education following immigration appears to confer a compound benefit by raising the return to education acquired abroad

an optimization approach for supply chain management models with quantity discount policy abstract owing to the difficulty of treating nonlinear functions many supply chain management scm models assume that the average prices of materials production transportation and inventory are constant this assumption however is not practical vendors usually offer quantity discounts to encourage the buyers to order more and the producer intends to discount the unit production cost if the amount of production is large this study solves a nonlinear scm model capable of treating various quantity discount functions simultaneously including linear single breakpoint step and multiple breakpoint functions by utilizing the presented linearization techniques such a nonlinear model is approximated to a linear mixed 0 1 program solvable to obtain a global optimum

side payment contracts in two person nonzero sum supply chain games review discussion and applications this paper investigates supply chain coordination with side payment contracts we first summarize specific side payment contracts and present our review on the literature that developed general side payment schemes to coordinate supply chains following our review we discuss two criteria that a proper side payment contract must satisfy and accordingly introduce a decision dependent transfer payment function and a constant transfer term we present the condition that the transfer function must satisfy and use nash arbitration scheme and shapley value to compute the constant transfer term and derive its closed form solution next we provide a five step procedure for the development of side payment contract and apply it to four supply chain games cournot and bertrand games a two retailer supply chain game with substitutable products and a one supplier one retailer supply chain more specifically for the cournot game we construct a linear transfer function and a constant side payment to coordinate two producers for the bertrand game we build a nonlinear transfer function which is equivalent to a revenue sharing contract and show that the constant term is zero and two firms in the game equally share the system wide profit for a supply chain with substitutable products we present a side payment contract to coordinate two retailers for a two echelon supply chain we develop a proper side payment scheme that can coordinate the supply chain and also help reduce the impact of forward buying on supply chain performance

do in work tax credits serve as a safety net we test the eitc s response to economic need using irs data we exploit differences in timing and severity of economic cycles across states because the eitc requires earned income there is a theoretical ambiguity in the credit s cyclicality we find higher unemployment leads to increased likelihood of eitc recipiency and in credit amounts received for married couples but has insignificant effects for single individuals the eitc s protective effects are concentrated among skilled workers the eitc mitigates income shocks for married couples with children and groups likely to have moderate earnings but does not for most recipients single parents with children

poverty in america trends and explanations despite robust growth in real gdp per capita in the last three decades u s poverty rates have changed very little we summarize some basic facts about poverty in the united states relying on a combination of previously published data from the census bureau and our own tabulations based on current population survey data we then discuss and evaluate four determinants of changes in the poverty rate that have been advanced in the literature the impact of labor market opportunities the role of changes in family structure the role played by government antipoverty programs and the role of immigration

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

dynamic lot sizing with batch ordering and truckload discounts this paper studies two important variants of the dynamic economic lot sizing problem that are applicable to a wide range of real world situations in the first model production in each time period is restricted to a multiple of a constant batch size where backlogging is allowed and all cost parameters are time varying several properties of the optimal solution are discussed based on these properties an efficient dynamic programming algorithm is developed the efficiency of the dynamic program is further improved through the use of monge matrices using the results developed for the first model an o n3log n algorithm is developed to solve the second model which has a general form of product acquisition cost structure including a fixed charge for each acquisition a variable unit production cost and a freight cost with a truckload discount this algorithm can also be used to solve a more general problem with concave cost functions

coordinated decisions for substitutable products in a common retailer supply chain abstract this paper studies coordination mechanisms in a supply chain which consists of two suppliers with capacity uncertainties selling differential yet substitutable products through a common retailer who faces price sensitive random demand of these two products we develop in a noncompetitive setting three coordination models revenue sharing return policy and combination of revenue sharing and return policy and contrast them with a basic and uncoordinated model we are able to establish the ordinal relationship among the retailer s ordering and pricing decisions and analytically compare the performances between certain models when two suppliers are identical we find that the retailer s ordering and pricing decisions in the model with return policy in the case of identical suppliers are independent of demand or supply uncertainty our numerical results reveal that the performances of coordination models in the case of nonidentical suppliers resemble those in the case of identical suppliers we find that the retailer will place a larger order quantity in models where her average cost per unit sold is smaller we also find that product substitutability and uncertainties have different effects on chain performances

lot sizing for products with finite demand horizon and periodic review inventory policy abstract this paper analyzes and develops an efficient algorithm for solving a simple generalization of the classical economic order quantity eoq model where the demand horizon is finite and a periodic review inventory policy is followed such problems could arise in production shops where the product under consideration is going to be discontinued and or replaced by some other product after a certain known number of periods such problems could also arise as subproblems in large prodution inventory problems were demand rate is constant in some periods and varying in others

an optimal solution technique to the single vendor multi buyer integrated inventory supply chain by incorporating some realistic factors abstract this paper develops two generalized integrated inventory models to deliver a single product from a vendor to multiple buyers to minimize the total cost of set up ordering inventory holding and transportation the production flow is synchronized by transferring the lot with equal and or unequal either all are equal or all are unequal or a combination of equal and unequal sized batches sub lots each of which incurs a transportation cost for easy implementation of the models we relax some unrealistic assumptions in the existing models such as unlimited capacities of the transport equipment and buyers storage insignificant set up and transportation times unlimited lead time and batch sizes a common optimal solution technique to the models is derived and their performances are analyzed potential significances of the solution method are highlighted with solutions of some numerical problems the importance of the relaxed factors and limitation of the models are discussed

labor mobility of immigrants training experience language and opportunities summary statistics observations percent mean sdschooling 419 14 58 2 74age on arrival 419 38 05 9 15white collar in fsu 284 67 78 blue collar in fsu 127 30 31 did not work in fsu 8 1 91 married 363 86 63 english 419 1 76 0 94hebrew before migration 50 11 93 ulpan attendance 386 92 12 ulpan completion 332 79 24 ulpan length months 387 5 61 1 34hebrew1 rst survey 419 2 71 0 82hebrew2 second survey 316 2 98 0 83t able a2 transitions between the labor market states quarters 8 9quarters 3 4 wc bc wt bt ue obs wc 79 57 10 75 3 23 2 15 4 30 93bc 2 58 80 80 1 72 2 87 12 03 349wt 51 28 28 21 0 00 0 00 20 51 39bt 23 81 52 38 0 00 0 00 23 81 21ue 18 93 47 93 6 51 1 78 24 85 169quarters 14 15quarters 8 9 wc bc wt bt ue obs wc 90 52 6 90 0 00 0 86 1 72 116bc 4 56 90 88 0 35 0 70 3 51 285wt 41 18 41 18 0 00 0 00 17 65 17bt 25 00 66 67 0 00 0 00 8 33 12ue 23 86 44 32 0 00 0 00 31 82 88quarters 18 19quarters 14 15 wc bc wt bt ue obs wc 96 72 3 28 0 00 0 00 61bc 2 47 90 12 2 47 4 94 81wt bt 0 00 100 00 0 00 0 00 1ue 30 00 20 00 0 00 50 00 10

optimal centralized ordering policies in multi echelon inventory systems with correlated demands this paper treats a depot warehouse system in which demand occurs at the warehouse or retail level this work differs from a number of other studies in that we allow item demands to be correlated both across warehouses and also correlated in time our motivation for this generalization arises from our experience with an actual system of this type used by a major national producer and distributor of consumer products we observed both high correlations between successive monthly demands around 0 7 and correlations between demands for an item at different locations also about 0 7 in a given time period we derive an explicit expression for the optimal safety stock as a function of the level of correlation through time the analysis requires two assumptions 1 the allocation assumption and 2 the equal coefficient of variation assumption similar assumptions have been used by other researchers finally numerical evaluations are included to illustrate the impact of the various magnitudes of correlation

a cooperative inventory policy with deteriorating items for a two echelon model a cooperative inventory policy between supplier and buyer is proposed unlike other studies we consider the case of deteriorating items and permit the completed back order in the problem we solve the problem without the condition of equal replenishments periods during a specified planning horizon and present a procedure to find the optimal solution a case is presented to demonstrate the application of the proposed approach the sensitivity analysis for a cooperation policy between supplier and buyer also are explored

note a note on the dynamic lot size model with uncertainty in demand and supply processes in this paper we give some extensions of a result of nevison and burstein nevison c h m burstein 1984 the dynamic lot size model with stochastic lead times management sci 30 100 109 who discuss a dynamic lot sizing model with stochastic lead times they consider a situation in which the lead time distribution is unaltered by the amount which is ordered but is otherwise arbitrary and characterize the optimal solution in terms of points at which there is zero inventory here we give a more precise characterization and show that these results can be extended to a situation in which the demands are also stochastic and in which there is uncertainty relating to quantity as well as to the timing of demands and order arrivals the method of proof that we use is different from that used by nevison and burstein

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

an integrated vendor buyer inventory model with order processing cost reduction and permissible delay in payments trade credit plays an important role in financing for many businesses and industries for the buyers purchased inventory can be considered to be financed in whole or in part with permissible delay in payments during the purchasing process on the other hand both the vendor and buyer take part in order processing cost reduction by applying information technologies such as edi electronic data interchange the order processing cost can also be reduced by adding certain capital investments and this will affect the lot size decisions this article develops an integrated inventory model to determine the optimal inventory policy under conditions of order processing cost reduction and permissible delay in payments and shows that the total annual variable cost function possesses some kinds of convexities a solution procedure is provided to determine the optimal order policy finally a numerical example is presented to illustrate the solution procedure

lot sizing in a serial distribution system with capacitated in system production flow abstract in this paper we focus on an n stage serial production distribution system with limited production capacity at the first stage our objective in such a system is to find inventory management policies that minimize the global logistic cost including transportation and holding costs we use myopic heuristics based on the breakdown of the system into local systems one of these systems is a 2 stage system and the second is a 3 stage system they both can be solved with a very good performance guarantee the successive optimizations of such systems provide quite good policies for the global system as asserted by the experimental results at the end of the paper

supply chain coordination perspectives empirical studies and research directions supply chains sc are generally complex and are characterized by numerous activities spread over multiple functions and organizations which pose interesting challenges for effective sc coordination to meet these challenges sc members must work towards a unified system and coordinate with each other a systematic literature review is presented in this paper to throw light on the importance of sc coordination the objectives of this paper are to report and review various perspectives on sc coordination issues understand and appreciate various mechanisms available for coordination and identify the gaps existing in the literature a framework is suggested indicating scope for further research

optimal production inventory policy for an integrated multi stage supply chain with time varying demand abstract an integrated multi stage supply chain with time varying demand over a finite planning horizon is considered in this paper the objective is to devise the optimal production inventory policy to minimize the total operational cost the model is formulated as a mixed integer nonlinear programming problem the problem is represented as a weighted directed acyclic graph the global minimum total operational cost is computed in polynomial time by the developed algorithm two numerical examples of a seasonal product and a product over its life cycle are studied to illustrate the results a sensitivity analysis of the system parameters is conducted to assist the supply chain decision makers

dynamic version of the economic lot size model this article originally appeared in management science october 1958 volume 5 number 1 pp 89 96 published by the institute of management sciences a forward algorithm for a solution to the following dynamic version of the economic lot size model is given allowing the possibility of demands for a single item inventory holding charges and setup costs to vary over n periods we desire a minimum total cost inventory management scheme which satisfies known demand in every period disjoint planning horizons are shown to be possible which eliminate the necessity of having data for the full n periods

three echelon supply chain coordination considering duopolistic retailers with perfect quality products abstract this paper explores channel coordination and profit division issues of a manufacturer distributer duopolistic retailers supply chain for a product where the manufacturer supplies lotsize of the product that contains a random portion of imperfect quality item in manufacturer stackelberg vertical game setting the duopolistic retailers three behaviours cournot collusion and stackelberg are discussed besides analyzing the effect of imperfect quality product on optimal decisions the paper depicts the hybrid contract mechanism so that all units quantity discount with franchise fee resolves channel conflict though unable to provide win win outcome for surplus profit division the paper proposes two sequential bargaining processes backward and forward where outcome of a nash bargaining is dependent on the previous it is found that for channel coordinated win win profit the manufacturer prefers collusion stackelberg and cournot while the retailer prefers the reverse and both prefer backward sequential bargaining but the distributers preference depends on the target profit that it sets during the bargaining process the proposed mechanisms are illustrated by a numerical example

the integrated management of logistic chains in the white goods industry a field research in italy after having devoted many e orts and investments in improving their internal capacity to produce the right product at the right price at the right time companies are now starting to discover that much of the value they deliver to their customers depends not only on their own performance but also on the performance of all the other companies that belong to the same logistic chain thus the integrated management of logistic chains has gained a large attention in the latest years as one of the most e ective tools to achieve an overall improvement in the economic as well as in the logistic value that is embodied in each product this paper presents some results of a eld research focused on logistic chain management carried on by means of direct interviews on a sample of italian companies shops and nal customers belonging to the white goods industry questions highlight the main cost and logistic e ects that arise among di erent tiers of the chain when they interact here we illustrate the used methodology moreover we discuss some of the empirical results achieved with the aim of assessing the improvement potential that a tighter integration could achieve in particular it is shown that wide space for improving companies pro tability is available both by reducing costs and by increasing sales 2001 elsevier science b v all rights reserved

the more things change the more they stay the same the safety net and poverty in the great recession much attention has been given to the large increases in safety net spending during the great recession we examine the relationship between poverty the safety net and business cycles historically and test whether there has been a significant change in this relationship we find that post welfare reform temporary assistance for needy families did not respond during the great recession and extreme poverty is more cyclical than in prior recessions food stamps and unemployment insurance are providing more protection or no less protection in the great recession and there is some evidence of less cyclicality for 100 poverty

the impact of family income on child achievement evidence from the earned income tax credit using an instrumental variables strategy we estimate the causal effect of income on children s math and reading achievement our identification derives from the large nonlinear changes in the earned income tax credit the largest of these changes increased family income by as much as 20 percent or approximately 2 100 between 1993 and 1997 our baseline estimates imply that a 1 000 increase in income raises combined math and reading test scores by 6 percent of a standard deviation in the short run test gains are larger for children from disadvantaged families and robust to a variety of alternative specifications jel h24 h31 i21 i38 j13

welfare the earned income tax credit and the labor supply of single mothers during 1984 1996 welfare and tax policy were changed to encourage work by single mothers the earned income tax credit was expanded welfare benets were cut welfare time limits were added and welfare cases were terminated medicaid for the working poor was expanded as were training programs and child care during this same time period there were unprecedented increases in the employment and hours of single mothers we show that a large share of the increase in work by single mothers can be attributed to the eitc and other tax changes with smaller shares for welfare benet cuts welfare waivers training programs and child care programs