perishable inventory theory a review this paper reviews the relevant literature on the problem of determining suitable ordering policies for both fixed life perishable inventory and inventory subject to continuous exponential decay we consider both deterministic and stochastic demand for single and multiple products both optimal and sub optimal order policies are discussed in addition a brief review of the application of these models to blood bank management is included the review concludes with a discussion of some of the interesting open research questions in the area

macro economic stability and policy rules in a two sector model of an open economy purchasing power parity exchange rate rules are often used in open economies to stabilize the demand for exports and domestic output r dornbusch 1982 shows tha t such rules may increase the variability of output via the supply si de by destabilizing the price of imported intermediate goods here a two sector wage spillover model is employed to demonstrate that this result is more likely because although exchange rate indexation woul d decrease the variability of output in the traded goods sector it m ay increase the variability of output in the nontraded goods sector a nd in the aggregate via the wage linkage between sectors

an optimization approach for managing fresh food quality throughout the supply chain one of the most challenging tasks in today s food industry is controlling the product quality throughout the food supply chain in this paper we integrate food quality in decision making on production and distribution in a food supply chain we provide a methodology to model food quality degradation in such a way that it can be integrated in a mixed integer linear programming model used for production and distribution planning the resulting model is applied in an illustrative case study and can be used to design and operate food distribution systems using both food quality and cost criteria

an milp approximation for ordering perishable products with non stationary demand and service level constraints abstract we study the practical production planning problem of a food producer facing a non stationary erratic demand for a perishable product with a fixed life time in meeting the uncertain demand the food producer uses a fifo issuing policy the food producer aims at meeting a certain service level at lowest cost every production run a setup cost is incurred moreover the producer has to deal with unit production cost unit holding cost and unit cost of waste the production plan for a finite time horizon specifies in which periods to produce and how much we formulate this single item single echelon production planning problem as a stochastic programming model with a chance constraint we show that an approximate solution can be provided by an milp model the generated plan simultaneously specifies the periods to produce and the corresponding order up to levels the order up to level for each period is corrected for the expected waste by explicitly considering for every period the expected age distribution of the products in stock the model assumes zero lead time and backlogging of shortages the viability of the approach is illustrated by numerical experiments simulation shows that in 96 4 of the periods the service level requirements are met with an error tolerance of 1

public versus private investment in human capital endogenous growth and income inequality in this paper we present an overlapping generations model with heterogeneous agents in which human capital investment through formal schooling is the engine of growth we use simple functional forms for preferences technologies and income distribution to highlight the distinction between economies with public education and those with private education we find that income inequality declines more quickly under public education on the other hand private education yields greater per capita incomes unless the initial income inequality is sufficiently high we also find that societies will choose public education if a majority of agents have incomes below average

reducing emissions in transportation and inventory management r q policy with considerations of carbon reduction abstract in this study we examine three approaches on the effects of controlling carbon emissions in transportation and inventory management a business as usual scenario model bausm which delineates how carbon footprints from inventory storage and related transportation are captured is firstly developed as the benchmark model based on bausm we then develop three models with different carbon reduction approaches the first one is constructed by adding a constraint to represent the percentage target of emission reduction the second one integrates carbon taxes or cap and trade scheme into inventory management and the last one takes both reduction target and carbon offset opportunities into account our work provides new analytical models which integrate cost and emissions in transportation and storage under the framework of continuous inventory review r q policy for stochastic demand optimization algorithms are developed for solving models and related properties are investigated to examine the effects of carbon reduction and associated costs of three models the policy implications of the models are examined and discussed to provide insights for reference of the practitioners and the policy makers

competition between private and public schools vouchers and peer group effects a theoretical and computational model with tax financed tuition free public schools and competitive tuition financed private schools is developed students differ by ability and income achievement depends on own ability and on peers abilities equilibrium has a strict hierarchy of school qualities and two dimensional student sorting with stratification by ability and income in private schools high ability low income students receive tuition discounts while low ability high income students pay tuition premia tuition vouchers increase the relative size of the private sector and the extent of student sorting and benefit high ability students relative to low ability students

exchange rate rules and macroeconomic stability this paper discusses exchange rate rules in their role as macroeconomic instruments we abstract throughout from the trend part of exchange rate behaviour a crawling peg necessitated by differences in trend inflation and emphasise instead the implications of exchange rate rules in providing flexibility of real wages or in affecting the stability of output or prices

a new class of stock level dependent ordering policies for perishables with a short maximum shelf life many perishables such as fresh food and blood platelet concentrates are characterized by a short maximum shelf life as demand is often highly uncertain the outdating and shortages figures can be very high especially when frequent replenishment is not possible or inefficient due to fixed ordering cost we present a new class of stock level dependent ordering policies the s s q q policy which is a periodic review s s policy with the order quantity restricted by a minimum q and maximum q optimal weekday dependent parameter values are derived by dynamic programming and simulation the s s q q policy performs nearly optimal and improves the s s policies in many cases by 4 25

centralization fiscal federalism and private school attendance a cge model is used to analyze the impact of public school financing on private school attendance the common perception that public school finance centralization will necessarily lead to greater private school attendance is not correct in such a model even when that centralization involves an extreme equalization as in california furthermore if centralization is less dramatic as in most states declines in private school attendance are even more pronounced this weakens the speculation that low exit rates to private schools in centralizing states imply that general public school quality does not drop as a result of such centralization

does school tracking affect equality of opportunity new international evidence this paper investigates whether the interaction between family background and secondary school tracking affects human capital accumulation a widely shared view is that more tracking reinforces the role of parental privilege and thereby reduces equality of opportunities this may occur for several reasons including peer effects more talented students are gathered together teacher sorting better teachers prefer teaching better students differences in curricula academic oriented schools like the german gymnasium the french lycee the british grammar school or the italian liceo teach abilities that increase the probability of entering college and or differences in resource endowment compared to the current literature which focuses on early outcomes such as test scores at 13 and 15 years old we look at later outcomes including literacy dropout rates college enrolment employability and earnings while we do confirm the common view that school tracking reinforces the impact of family background when looking at educational attainment and labour market outcomes we do not confirm the same results when studying its impact on literacy and on the job training overall school tracking has an ambiguous effect in our sample of countries on the one hand and consistently with the previous literature tracking has a detrimental impact on educational attainment because it prevents some individuals from further progressing to the tertiary level of education the diversion effect on the other hand the curricula offered in vocational schools seem more effective in promoting further training and adult competences the specialization effect thereby reducing the impact of parental background on these two outcomes thus reducing the extent of student tracking either by raising the age of first selection or by reducing the number of tracks available may be appropriate for increasing intergenerational mobility in educational attainment but may increase social exclusion for people from disadvantaged backgrounds giorgio brunello and daniele checchi

cross country differences in intergenerational earnings mobility international studies of the extent to which economic status is passed from one generation to the next are important for at least two reasons first each study of a particular country characterizes an important feature of that country s income inequality second comparisons of intergenerational mobility across countries may yield valuable clues about how income status is transmitted across generations and why the strength of that intergenerational transmission varies across countries the e rst section of this paper explains a benchmark measure of intergenerational mobility commonly used in u s studies the second section summarizes comparable empirical e ndings that have accumulated so far for countries other than the united states the third section sketches a theoretical framework for interpreting cross country differences in intergenerational mobility

review of inventory systems with deterioration since 2001 abstract this paper presents an up to date review of the advances made in the field of inventory control of perishable items deteriorating inventory the last extensive review on this topic dates back to 2001 goyal s k and giri b c recent trends in modeling of deteriorating inventory european journal of operational research 134 1 16 since then over two hundred articles on this subject have been published in the major journals on inventory control indicating the need for a new review we use the classification of goyal and giri based on shelf life characteristics and demand characteristics contributions are highlighted by discussing main system characteristics including price discounts backordering or lost sales single or multiple items one or two warehouses single or multi echelon average cost or discounted cash flow and payment delay

intergenerational income mobility in the united states social scientists and policy analysts have long expressed concern about the extent of intergenerational income mobility in the united states but remarkably little empirical evidence is available the few existing estimates of the intergenerational correlation in income have been biased downward by measurement error unrepresentative samples or both new estimates based on intergenerational data from the panel study of income dynamics imply that the intergenerational correlation in long run income is at least 0 4 indicating dramatically less mobility than suggested by earlier research copyright 1992 by american economic association

an allocation and distribution model for perishable products this paper presents an allocation model for a perishable product distributed from a regional center to a given set of locations with random demands we consider the combined problem of allocating the available inventory at the center while deciding how these deliveries should be performed two types of delivery patterns are analyzed the first pattern assumes that all demand points receive individual deliveries the second pattern subsumes the frequently occurring case in which deliveries are combined in multistop routes traveled by a fleet of vehicles computational experience is reported

ability tracking school competition and the distribution of educational benefits abstract to study the effects of ability grouping on school competition we develop a theoretical and computational model of tracking in public and private schools we examine tracking s consequences for the allocation of students of differing abilities and income within and between public and private schools private schools tend to attract the most able and wealthiest students and rarely track in equilibrium public sector schools can maximize attendance by tracking students public schools retain a greater proportion of higher ability students by tracking but lose more wealthy lower ability students to the private sector consequently socioeconomic status is a predictor of track assignment in public schools for the entire population public sector tracking has small aggregate effects on achievement and welfare but results in significant redistribution from lower to higher ability students

mobility targeting and private school vouchers simulations are derived from a three district model of low middle and highincome school districts calibrated to new york data with housing stocks that vary within and across districts in this model it is demonstrated that school district targeted vouchers are similar in their impact to nontargeted vouchers but vastly different from vouchers targeted to low income households furthermore strong migration effects are shown to significantly improve the likely equity consequences of voucher programs jel 122 128 h73 persistent frustration with the perceived low quality of public education exacerbated by concerns over the inherently unequal levels of public school quality across school districts has caused policy makers courts and researchers to investigate modifications and alternatives to the current public school system one idea that has received increasing academic and public attention is that of private school vouchers with proponents arguing that the competitive pressures of voucher programs would cause improvements in the efficiency of the publicschool system while at the same time addressing equity concerns if vouchers can be targeted to low income households or low income school districts but aside from a few limited experiments in some u s cities our experience with vouchers in the united states remains virtually nonexistent this limits the amount of information researchers can derive from standard empirical analysis in that it forces them to rely on only current nonvoucher induced differences in competition despite important suggestive results such work may not anticipate all the impacts from a large scale policy such as the voucher policies currently under discussion at the same time theoretical models of school finance are also limited in that they often either focus on only one particular aspect of the general equilibrium school finance problem or they are too rich and complex to yield crisp predictions

the desegregating effect of school tracking this paper makes the following point detracking schools that is preventing them from allocating students to classes according to their ability may lead to an increase in income residential segregation it does so in a simple model where households care about the school peer group of their children if ability and income are positively correlated tracking implies that some high income households face the choice of either living in the areas where most of the other high income households live and having their child assigned to the low track or instead living in lower income neighbourhoods where their child would be in the high track under mild conditions tracking leads to an equilibrium with partial income desegregation where perfect income segregation would be the only stable outcome without tracking

modeling an inventory routing problem for perishable products with environmental considerations and demand uncertainty the transition to sustainable food supply chain management has brought new key logistical aims such as reducing food waste and environmental impacts of operations in the supply chain besides the traditional cost minimization objective traditional assumptions of constant distribution costs between nodes unlimited product shelf life and deterministic demand used in the inventory routing problem irp literature restrict the usage of the proposed models in current food logistics systems from this point of view our interest in this study is to enhance the traditional models for the irp to make them more useful for the decision makers in food logistics management therefore we present a multi period irp model that includes truck load dependent and thus route dependent distribution costs for a comprehensive evaluation of co2 emission and fuel consumption perishability and a service level constraint for meeting uncertain demand a case study on the fresh tomato distribution operations of a supermarket chain shows the applicability of the model to a real life problem several variations of the model each differing with respect to the considered aspects are employed to present the benefits of including perishability and explicit fuel consumption concerns in the model the results suggest that the proposed integrated model can achieve significant savings in total cost while satisfying the service level requirements and thus offers better support to decision makers

tracking can be more equitable than mixing parents and policy makers often wonder whether and how the choice of a tracked or mixed educational system affects the equality of opportunity i answer this question by analyzing the influence of peers on future educational results i define an equal opportunity policy as one that maximizes the average lifetime income of the worst off type of individuals in society i e students from disadvantaged backgrounds i find that tracking maximizes average lifetime income if the opportunity cost of college attendance is sufficiently high

equity and efficiency in human capital investment the local connection a general model of community formation and human capital accumulation with social spillovers and decentralized school funding is used to analyse the causes of economic segregation and its consequences for equity and efficiency significant polarization arises from minor differences in endowments preferences or access to capital markets this makes income inequality more persistent across generations but the same need not be true for wealth equilibrium stratification tends to be excessive resulting in low aggregate surplus whether state equalization of school resources can remedy these problems hinges on how purchased social and family inputs interact in education and in mobility decisions

does the diversity of human capital increase gdp a comparison of education systems abstract this paper examines how different education systems affect gdp by influencing the diversity of human capital we construct an overlapping generation model in which agents are heterogeneous in income and innate ability and the final goods are produced with differentiated intermediate goods it is shown that under a realistic condition the diversity of human capital induced by income inequality always lowers the gdp of the next period while the diversity of human capital induced by heterogeneous ability can increase gdp if the produced intermediate goods are sufficiently substitutable and firms have a large span of control hence as public education equalizes education resources across households it mitigates the negative effect of income inequality on gdp while the effects of ability tracking crucially depend on the production structure of the economy

a hybrid l shaped method to solve a bi objective stochastic transshipment enabled inventory routing problem abstract recently greenness has become a very much needed condition in the transportation industry in this study we develop a green transshipment enabled model for the inventory routing problem irp in a many to one distribution network where demand for each product is realistically assumed to be uncertain the proposed framework is a bi objective stochastic programming model the first objective function aims to minimize the expected value of the supply chain costs including inevitable shortage costs the second objective function aims to minimize the total quantity of the greenhouse gas ghg emission produced by the vehicles and disposed products we introduce a very practical innovative application of transshipment option to control transportation cost reduce ghg emissions and absorb the uncertainty in order to solve the proposed model an efficient hybrid algorithm combining l shaped method a sort of decomposition approach for stochastic optimization and compromise programming a well known approach for multi objective optimization is proposed the results show that how companies can make a reasonable tradeoff between the cost and environmental concerns and emphasize the role of transshipment option as a lever to improve both economic and environmental performance and absorb the demand fluctuations

school tracking and intergenerational income mobility evidence from the finnish comprehensive school reform abstract this paper estimates the effect of a major education reform on intergenerational income mobility the finnish comprehensive school reform of 1972 1977 replaced the old two track school system with a uniform nine year comprehensive school and shifted the selection of students to vocational and academic tracks from age 11 to age 16 we estimate the effect of this reform on the intergenerational income elasticity using a representative sample of males born between 1960 and 1966 the identification strategy relies on a differences in differences approach and exploits the fact that the reform was implemented gradually across the country during a six year period the results indicate that the reform reduced the intergenerational income elasticity by 23 from the pre reform elasticity of 0 30 to post reform elasticity of 0 23

modelling food logistics networks with emission considerations the case of an international beef supply chain intrinsic characteristics of food products and processes along with growing sustainability concerns lead to the need for decision support tools that can integrate economic considerations with quality preservation and environmental protection in food supply chains in this study we develop a multi objective linear programming molp model for a generic beef logistics network problem the objectives of the model are i minimizing total logistics cost and ii minimizing total amount of greenhouse gas emissions from transportation operations the model is solved with the ee constraint method this study breaks away from the literature on logistics network models by simultaneously considering transportation emissions affected by road structure vehicle and fuel types weight loads of vehicles traveled distances return hauls and product perishability in a molp model we present computational results and analysis based on an application of the model on a real life international beef logistics chain operating in nova andradina mato grosso do sul brazil and exporting beef to the european union trade off relationships between multiple objectives are observed by the derived pareto frontier that presents the cost of being sustainable from the point of reducing transportation emissions the results from the pie chart analysis indicate the importance of distances between actors in terms of environmental impact moreover sensitivity analysis on practically important parameters shows that export ports capacities put pressure on the logistics system decreasing fuel efficiency due to the bad infrastructure has negative effects on cost and emissions and green tax incentives result in economic and environmental improvement

peer group effects and educational attainment abstract given the aims of an educational system the relationship between educational inputs and educational outputs the educational production function a frequency distribution of students by ability and a fixed educational budget how should students and educational expenditures be allocated over classrooms the paper focuses on peer group effects which capture the influence of a student s classmates on his educational attainment and the determinants of whether streaming or mixing is preferable it should be noted that peer group effects arise in other contexts notably in the workplace thus the paper casts some light on the optimal composition of teams

heterogeneity stratification and growth macroeconomic implications of community structure and school finance this paper examines how socioeconomic stratification and alternative systems of education finance affect inequality and growth agents interact through local public goods or externalities school funding neighborhood effects and economywide linkages complementary skills knowledge spillovers sorting families into homogeneous communities often minimizes the costs of existing heterogeneity but mixing reduces heterogeneity faster integration therefore tends to slow down growth in the short run yet raise it in the long run a move to state funding of education presents society with a similar intertemporal trade off local and global complementarities play major roles in determining the efficient social and educational structures copyright 1996 by american economic association

a two stage stochastic programming model for inventory management in the blood supply chain managing inventories in the blood supply chain is a challenging task mainly due to the uncertain nature of the demand for blood units the perishable nature of the blood and a strong subjective bias towards criteria other than cost minimisation in this paper we propose a two stage stochastic programming model for defining optimal periodic review policies for red blood cells inventory management that focus on minimising operational costs as well as blood shortage and wastage due to outdating taking into account perishability and demand uncertainty the adoption of this framework allows the consideration of more general stochastic processes to model the demand uncertainty than approaches currently available in literature moreover this framework renders a model that can be solved efficiently by general purpose off the shelf optimisation software to illustrate the potential benefits of adopting the proposed model to support the definition of optimal blood inventory control policies a case study is presented considering realistic data representing the daily demand for blood which was generated using the average and standard deviation of the demand for eight types of blood results suggest meaningful insights concerning practices that could lead to improvement in the blood supply chain performance in particular we observed that it would be possible to revise the current inventory control policies by reducing current target levels to diminish wastage and total cost without compromising the service level finally the consideration of blood substitutions showed further improvement in the performance of the blood inventory management system