explaining the deteriorating entry earnings of canada s immigrant cohorts 1966 2000 abstract using the 1981 1986 1991 1996 and 2001 canadian censuses we explore causes of the deterioration in entry earnings of successive cohorts of immigrant men and women roughly one third of the deterioration is explained by compositional shifts in language ability and region of birth we find no evidence of a decline in the returns to foreign education for either immigrant men or immigrant women but a definite deterioration in the returns to foreign labour market experience most strongly among men from non traditional source countries we can explain roughly two thirds of the male and one half of the female deterioration without any reference to entry labour market conditions when we also account for entry conditions our results suggest canada s immigrants of the late 1990s would otherwise have enjoyed entry earnings equal to or higher than their counterparts of the 1960s

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

bundles duties and rights a revised framework for analysis of natural resource property rights regimes in their 1992 paper schlager and ostrom presented a property rights framework characterized by nested cumulative attributes it has become arguably the most ubiquitous framework for analysis of natural resources and property rights we revisit their contribution and discuss how the framework could evolve to address increasingly complex situations with particular attention to institutional change we devote increased attention to duties and liabilities associated with right allocation tying the framework to a broader property rights literature we conclude with an application to reducing emissions from deforestation and forest degradation redd illustrating how revisions to the framework facilitate contemporary institutional analysis

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

dynamic uncapacitated lot sizing with random demand under a fillrate constraint abstract this paper deals with the single item dynamic uncapacitated lot sizing problem with random demand we propose a model based on the static uncertainty strategy of bookbinder and tan 1988 in contrast to these authors we use exact expressions for the inventory costs and we apply a fillrate constraint we present an exact solution method and modify several well known dynamic lot sizing heuristics such that they can be applied for the case of dynamic stochastic demands a numerical experiment shows that there are significant differences in the performance of the heuristics whereat the ranking of the heuristics is different from that reported for the case of deterministic demand

the impact of language ability on employment and earnings of britain s ethnic communities the fourth national survey of ethnic minorities contains useful information about the language ability of britain s non whites as well as a wealth of comparative information for whites the paper attempts to establish how much of the lower unemployment and higher earnings enjoyed by whites is the result of a comparative advantage in language language is shown to contribute to a part of the non white disadvantage but after language effects are removed non whites males still have higher unemployment rates and lower earnings language disadvantage among non white females leads to higher inactivity rates rather than more unemployment

blood platelet production with breaks optimization by sdp and simulation abstract the production and inventory management of blood products at blood banks and hospitals is a problem of general human interest as a shortage may put lives at risk shortages are to be kept to a minimum as the supply is voluntary and costly any spill of unused blood products is also to be minimized blood platelets thrombocytes which are the most expensive and perishable blood product have the complication of a limited shelf life of only 5 7 days a general figure in the western world the usa and western europe for the spill of blood platelets is in the order of 15 20 a combined new approach is therefore presented which combines stochastic dynamic programming sdp and simulation to provide i practical simple order up to rules that are nearly optimal ii formal theoretical support the approach has been applied to a dutch regional blood bank numerical results show a significant reduction of the figures from 1 to 1 for shortages 20 to 1 for spill a practical question for blood bank managers that still remains is how to anticipate irregular production breaks like at easter and christmas the present paper therefore will extend the combined sdp simulation approach to include such breaks the main findings are also for these breaks a simple order up to rule remains to be nearly optimal also for these breaks the outdating and shortages can be kept less than 1 the stationary periods with production and the non stationary breaks without can be integrated the approach thus seems suitable for practical implementation

mergers and acquisitions in blood banking systems a supply chain network approach blood banking systems in the united states over the past decade have been faced with a volatile demand for blood specifically a decrease in demand for red blood cells for a variety of reasons this change in the blood supply chain landscape accompanied by an increasing emphasis on cost efficiency is a driver of mergers acquisitions between blood banks in this paper we first present supply chain network optimization pre and post merger models the models handle perishability of the life saving product of blood include both operational and discarding costs of waste capture the uncertainty associated with the demand points as well as the expected total blood supply shortage cost and the total discarding cost at demand points they also incorporate capacities on the links their solution yields the optimal path and link flows plus the frequencies of activities associated with blood collection shipment testing and processing storage and distribution and incurred total costs we provide a cost efficiency synergy measure associated with a merger or acquisition in the blood banking industry as well as measures capturing the expected supply shortage and surplus the methodological framework and its applicability are then illustrated via a large scale blood supply chain network example inspired by a pending merger in the real world in both status quo and disaster scenarios

the endogeneity between language and earnings international analyses this study is concerned with the determinants of dominant language fluency its effects on earnings and its endogeneity with earnings among immigrants dominant language fluency is hypothesized to

heterogeneous immigrants and foreign direct investment the role of language skills we investigate the interplay of language skills and immigrant stocks in determining bilateral fdi out stocks of oecd reporting countries applying a poisson panel estimator to 2004 2011 data we find a robust positive effect of bilateral immigrants on bilateral fdi provided that residents of the two countries have few language skills in common we find a similar effect for immigrants from third countries that speak the language s of the fdi host country making them potential substitutes for bilateral migrants our findings suggest that immigrants facilitate outgoing fdi through their language skills rather than through other characteristics like cultural familiarity

replenish up to inventory control policy with random replenishment intervals abstract the multi period inventory problems have been studied under two main assumptions continuous review assumption where an order can be made at any time depending on inventory position and periodic review assumption where an order can be initiated only at discrete time epochs in this study we analyze a multi period inventory problem that falls under neither of these two assumptions in the case we consider there are periodic replenishments but the replenishment intervals are taken to be i i d random variables this setting represents the real life cases where a supplier visits a retailer with random inter arrival times and the retailer replenishes his inventories based on a replenish up to level inventory control policy we also assume that only a certain fraction of unmet demand is backordered and the rest of it is lost in this setting under general distribution between replenishment epochs we show the concavity of the expected profit function and give the condition that must hold for the optimal replenish up to level we also present the specific solutions and analysis under two different distributions namely uniform and exponential distributions together with some numerical examples

property rights and liability for deforestation under redd implications for permanence in policy design reducing emissions from deforestation and forest degradation redd is critical in efforts to mitigate the effects of anthropogenic climate change despite uncertainty about the exact form of a future international redd system redd carbon property rights would need to be created and allocated with liability assigned for the potential loss of climate benefits in the event of carbon reversal from deforestation this commentary explores the links between forest property rights and liability to different redd policy options and their implications for permanence should national governments retain liability for permanence then project level activities that have individually assigned redd carbon rights may have a higher risk of carbon reversal than policies where rights are assigned to the state knowledge of pre existing forest rights is necessary for some policies implemented with government assigned redd rights in order to compensate for potential income losses from policy implementation

native language spoken language translation and trade we construct new series for common native language and common spoken language for 195 countries which we use together with series for common official language and linguistic proximity in order to draw inferences about 1 the aggregate impact of all linguistic factors on bilateral trade 2 the separate role of ease of communication as distinct from ethnicity and trust and 3 the contribution of translation and interpreters to ease of communication the results show that the impact of linguistic factors all together is at least twice as great as the usual dummy variable for common language resting on official language would say in addition ease of communication plays a distinct role apart from ethnicity and trust and so far as ease of communication enters translation and interpreters are significant finally emigrants have much to do with the role of ethnicity and trust in linguistic influence

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

language fluency and earnings estimation with misclassified language indicators we use panel data to analyze the determinants of speaking fluency and wages of immigrants our model takes account of two problems that may bias ols estimates of the impact of speaking fluency on earnings first subjective variables on an ordinal discrete scale such as self reported language ability can suffer from misclassification errors the model decomposes misclassification errors into a time persistent and a time varying component second the model accounts for correlated unobserved heterogeneity in language and earnings equation the main finding is that these two generalizations of the standard model both lead to substantial changes in the estimated effect of speaking fluency on earnings

order variability in perishable product supply chains abstract empirical research has shown that the degree of order variability in supply chains is significantly influenced by product and industry specific factors this paper analyzes the impact of perishability on order variability and the bullwhip effect in supply chains we decompose the ordering process of a retailer into a sales and an outdating process and quantify their short and long term variability and correlation we find differences to non perishable product supply chains driven by the impact of the inventory depletion policy stock out management and retailers service level requirement these three factors significantly affect the retailer s order variability and thus the decision making process and the profitability of the upstream supply stage for the majority of instances the perishable nature of a product results in the ordering process having a lower variability than the demand process only when inventory depletion is dominated by last in first out in high service level environments variability amplification can be observed we propose a dynamic ordering policy for the upstream supply stage taking into account negative correlation of retailer orders between periods this dynamic policy may lead to substantial performance improvements in a sensitivity analysis we investigate the impact of shelf life lead time and demand correlation

estimates of the economic returns to schooling from a new sample of twins this paper uses a new survey to contrast the wages of genetically identical twins with different schooling levels multiple measurements of schooling levels were also collected to assess the effect of reporting error on the estimated economic returns to schooling the data indicate that omitted ability variables do not bias the estimated return to schooling upward but that measurement error does bias it downward adjustment for measurement error indicates that an additional year of schooling increases wages by 12 to 16 percent a higher estimate of the economic returns to schooling than has been previously found copyright 1994 by american economic association

order quantities for perishable inventory control with non stationary demand and a fill rate constraint abstract we study the practical decision problem of fresh food production with a long production lead time to decide every period e g week how many items to produce when a batch is ready for use its items have a fixed shelf life after which the items become waste in the sense that they cannot be sold anymore the demand for fresh food products is uncertain and highly fluctuating mainly caused by price promotions of retail organisations we focus on cases where a so called cycle fill rate service level requirement applies we investigate the generation of a production plan that fixes the timing and quantity of the production for a finite time horizon to minimise waste one issues the oldest items first i e a fifo issuing policy in case of out of stock sales are lost we model this decision problem as a stochastic programming sp model the objective of our study is to find order quantities for the sp model that approximately meet cycle fill rate service level requirements while keeping outdating low to find approximate solutions for the sp model an milp model is developed the milp model is a deterministic approximation that generates feasible replenishment quantities in less than a second with a scenario based minlp approach optimal solutions are generated for a large sample of demand paths as a benchmark for the milp solutions we show that the milp model is suitable for practical use if the setup cost is such that the replenishment cycles in the production plan are close to or of the same length as the maximum shelf life in those cases the expected total costs are close to the costs of the optimal solution and the average fill rate is close to the required one

does compulsory school attendance affect schooling and earnings we establish that season of birth is related to educational attainment because of school start age policy and compulsory school attendance laws individuals born in the beginning of the year start school at an older age and can therefore drop out after completing less schooling than individuals born near the end of the year roughly 25 percent of potential dropouts remain in school because of compulsory schooling laws we estimate the impact of compulsory schooling on earnings by using quarter of birth as an instrument for education the instrumental variables estimate of the return to education is close to the ordinary least squares estimate suggesting that there is little bias in conventional estimates every developed country in the world has a compulsory schooling requirement yet little is known about the effect these laws have on educational attainment and earnings 1 this paper exploits an unusual natural experiment to estimate the impact of compulsory schooling laws in the united states the experiment stems from the fact that children born in different months of the year start school at different ages while compulsory schooling laws generally require students to remain in school until their sixteenth or seventeenth birthday in effect the interaction of school entry requirements and compulsory schooling laws compel students born

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

literacy and labour market outcomes self assessment versus test score measures this paper looks at the determinants of literacy and the relation between literacy and labour market outcomes while focusing on comparisons of self assessment versus test score measures of literacy the test score measure performs considerably better than the self assessments when literacy is treated as an outcome variable in terms of the overall fit of the model and the specific coefficient estimates with the self assessments sometimes actually generating wrongly signed parameters the test score measure also performs much better as an explanatory variable in the employment models with the self assessment variable generating significant underestimates of the effects of literacy on the probability of being employed finally the test score is also superior in the income models although the self assessment measure is at least a reasonably good performer in this regard suggesting that the main results reported in much of the existing literature based on such measures should perhaps be taken as good re

environmental entitlements dynamics and institutions in community based natural resource management abstract while community based natural resource management cbnrm now attracts widespread international attention its practical implementation frequently falls short of expectations this paper contributes to emerging critiques by focusing on the implications of intracommunity dynamics and ecological heterogeneity it builds a conceptual framework highlighting the central role of institutions regularized patterns of behavior between individuals and groups in society in mediating environment society relationships grounded in an extended form of entitlements analysis the framework explores how differently positioned social actors command environmental goods and services that are instrumental to their well being further insights are drawn from analyses of social difference new dynamic ecology new institutional economics structuration theory and landscape history the theoretical argument is illustrated with case material from india south africa and ghana

returns to foreign languages of native workers in the eu most papers on returns to languages are concerned with immigrants we use the european community household panel survey echp to infer returns on non native languages by non immigrants in nine countries of the european union we differ from the few other studies that deal with the same problem in three respects first we correct for time dependent measurement errors in self reporting as suggested by dustmann and van soest and find that the resulting iv estimates are much larger than those obtained by ols we also suggest that there is little room for time persistent errors and heterogeneity and that therefore our estimates should not suffer from the other usual biases secondly instead of using a dummy for each language we use the ratio of the population that is not proficient in a language in each country considered finally we estimate instrumental variable quantile regressions to illustrate how returns to languages vary at different points of the distribution of earnings

a supply chain network economic model with time based competition abstract this paper presents an integrated model for time cost competition between supply chains with heterogeneous customers the firms in our model can offer various time options for their production service to time sensitive customers this gives rise of a new concept of time based supply chain which we call t chain to be the basic element in the competition and extends the inter supply chain competition to a new dimension of time assuming the customers are heterogeneous in time cost bi criteria decision making we integrate the discrete choice theory into supply chain network competition and formulate the equilibrium conditions as a multinomial logit based variational inequality problem numerical examples are presented for model illustration and managerial insights such as profit maximization for a firm who participates in this supply chain network

property rights regimes and natural resources a conceptual analysis the term common property resource is an example of a term repeatedly used to refer to property owned by a government or by no one it is also used for property owned by a community of resource users such usage leads to confusion in scientific study and policy analysis in this paper we develop a conceptual schema for arraying property rights regimes that distinguishes among diverse bundles of rights ranging from authorized user to claimant to proprietor and to owner we apply this conceptual schema to analyze findings from a variety of empirical settings including the maine lobster industry

the effect of naturalization on wage growth a panel study of young male immigrants for young male immigrants naturalization facilitates assimilation into the u s labor market following naturalization immigrants gain access to public sector white collar and union jobs and wage growth accelerates consistent with removal of employment barriers the faster wage growth of immigrants who naturalize might alternatively result from greater human capital investment prior to naturalization stemming from a long term commitment to u s labor markets but there is no evidence that wage growth accelerates or the distribution of jobs improves until citizenship is attained finally the gains from naturalization are greater for immigrants from less developed countries and persist when we control for unobserved productivity

inventory models with minimal service level constraints abstract this paper investigates inventory models in which the stockout cost is replaced by a minimal service level constraint slc that requires a certain level of service to be met in every period the minimal service level approach has the virtue of simplifying the computation of an optimal ordering policy because the optimal reorder level is solely determined by the minimal slc and demand distributions it is found that above a certain critical service level the optimal s s policy collapses to a simple base stock or order up to level policy which is independent on the cost parameters this shows the minimal slc models to be qualitatively different from their shortage cost counterparts we also demonstrate that the imputed shortage cost transforming a minimal slc model to a shortage cost model does not generally exist the minimal slc approach is extended to models with negligible set up costs the optimality of myopic base stock policies is established under mild conditions

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