reducing the mean supply delay of spare parts using lateral transshipments policies lateral transshipment has been studied lately as a promising policy for increasing the performances of multi echelon spare parts inventory system by lateral transshipment spare parts can be moved from one location with excess inventory to another location at the same echelon in shortage with the aim of reducing supply delays of spare parts this paper will examine the relative effectiveness of two lateral shipments approaches in reducing the mean supply delay msd of a non repairable item with respect to a classical policy of no lateral shipments a simulation model of a two echelon supply network has been implemented and an experiment has been performed by varying different parameters of the supply network such as the number of warehouses locations at the lower echelon the supply lead time from the central depot the spare parts demand uncertainty and the size variability of the warehouses results show appreciable reductions of msd when lateral shipments are allowed with respect to the classical policy in almost every network configuration

the low skill trap recently it has become popular to argue that certain workers have fallen into a trap in which they have poor skills few job opportunities and a low return on training while others have not this paper demonstrates how such a trap can occur within a simple matching model with rent sharing rent sharing diminishes the worker s incentive to acquire skills however since firms also benefit from training rent sharing likewise induces job creation the subsequent improved matching prospects may offset the initial disincentive to invest however for this mechanism to be effective firms and workers must coordinate their actions if they do not the trap occurs

enhanced lateral transshipments in a multi location inventory system in managing an inventory network two approaches to the pooling of stock have been proposed reactive transshipments respond to shortages at a location by moving inventory from elsewhere within the network while proactive stock redistribution seeks to minimize the chance of future stockouts this paper is the first to propose an enhanced reactive approach in which individual transshipments are viewed as an opportunity for proactive stock redistribution we adopt a quasi myopic approach to the development of a strongly performing enhanced reactive transshipment policy in comparison to a purely reactive approach to transshipment service levels are improved while a reduction in safety stock levels is achieved the aggregate costs incurred in managing the system are significantly reduced especially so for large networks moreover an optimal policy is determined for small networks and it is shown that the enhanced reactive policy substantially closes the gap to optimality

competitive search equilibrium in this paper i construct an equilibrium for markets with frictions which is competitive in the sense that all agents are price takers and maximize utility subject to a set of market parameters i show that the equilibrium allocation is socially optimal i also show how the competitive search equilibrium can be achieved if employers with vacancies can advertise publicly the wages they pay

education ranking and competition for jobs i study workers incentives to invest in general human capital education in the presence of search induced unemployment workers queue for jobs and firms prefer to hire the most productive applicants because of rent sharing as a result an unemployed worker s ranking relative to other job seekers will influence his job finding rate this creates a rat race where workers invest in education partly in order to achieve a better ranking in equilibrium identical workers may have incentives to diversify in terms of education and the investments in education may exceed the socially optimal level

decision making for stock trading based on trading probability by considering whole market movement abstract risk in prediction for decision making should be taken into account this paper describes a method for decreasing the risk in decision making concerning individual events by considering the secondary information on the relationship between these individual events and the whole sequence of related events the proposed method is presented applied to the decision making in stock trading the trading probability is proposed for the prediction of the movement trend of an individual stock this probability is constructed on the predicted values of stock price returns and their volatility for this aim the relationship of movement trends between the individual stock and the whole stock market is taken into consideration a simulation study of stock trading has been performed by using this trading probability as the basic criterion of stock trading with actual stock data the results demonstrate that the proposed method leads with high certainty to a better profit than any isolated consideration of the whole stock market trend possible applications of the proposed method are also discussed

good jobs versus bad jobs this article develops a model of noncompetitive labor markets in which high wage good and low wage bad jobs coexist minimum wages and unemployment benefits shift the composition of employment toward high wage jobs because the composition of jobs in the laissez faire equilibrium is inefficiently biased toward low wage jobs these labor market regulations increase average labor productivity and may improve welfare

income distribution and macroeconomics this paper analyzes the role of wealth distribution in macroeconomics through investment in human capital it is shown that in the presence of credit markets imperfections and indivisibilities in investment in human capital the initial distribution of wealth affects aggregate output and investment both in the short and in the long run as there are multiple steady states this paper therefore provides an additional explanation for the persistent differences in per capita output across countries furthermore the paper shows that cross country differences in macroeconomic adjustment to aggregate shocks can be attributed among other factors to differences in wealth and income distribution across countries

combined demand and capacity sharing with best matching decisions in enterprise collaboration abstract demand and capacity sharing dcs among entities within a supply network are common practice and have become attractive strategies for competing and non competing supply enterprises ses examples include airlines test and assembly factories and outsourced maintenance and logistics providers the purpose maximize profit and resource utilization enable timely delivery to customers in spite of uncertain market demands and unexpected capacity shortages and maximize the overall stability dcs protocols are defined for the ses with capacity shortage known as demand sharing ses to utilize excess capacities of other ses known as capacity sharing ses thus fulfilling their current customers demand more effectively while eliminating excess inventory of capacity sharing ses these dcs roles vary over time high frequency of dcs decisions could impose additional costs to the collaborative network of ses cnse in terms of transactions negotiations and lateral transshipment of stocks between ses attention must be paid to the inevitable costs of collaboration for dcs best matching bm protocol is proposed to minimize the dcs costs through dynamic matching of ses and customers with respect to the customers demand and ses available capacity to share bm protocol is also applied for finding the best matches between dcs proposals during collaboration negotiations among ses a novel mixed integer programming mip formulation is developed for modeling and analyzing the combined dcs bm decisions the dcs bm model is then validated using the queuing theory it is shown mathematically and through numerical experiments that the dcs bm model 1 outperforms the previous non collaborative models in terms of resource utilization and stability and 2 provides a dominating strategy compared with both collaborative and non collaborative models for optimizing the total cnse profit and service level

equilibrium wage dispersion and interindustry wage differentials this paper develops a search theoretic explanation of interindustry wage differentials given coordination problems in the labor market the probability of filling a vacancy is an increasing function of the wage offered in equilibrium firms that find vacancies more costly will offer higher wages the model thus explains the persistence of interindustry wage differentials and their correlation with industry average capital labor ratio and profitability additionally the model predicts that high wage firms will receive more applications per job opening and that wages in the labor market will behave as strategic complements

frictional assignment i efficiency abstract this paper examines the two sided matching problem where the agents on each side of the market are heterogeneous and the matching process is time consuming this is cast in a labor market setting where workers of different skills match with different machine qualities i characterize the efficient allocation and then show that it can be decentralized by a market mechanism the efficient assignment is not always positively assortative despite the fact that machine qualities and skills are complementary in production to decentralize the efficient allocation the market mechanism requires the firms to post wages and commit each machine quality to a particular skill implications on wage inequality are briefly examined journal of economic literature classification numbers j31 e24 j64

efficient ways to finance human capital investments standard theory predicts that if wages are determined by bargaining workers underinvest in human capital as they bear all the investment costs yet receive only a share less than one of the return i show that this result depends on the way the investments are financed i introduce contingent loans which do not accumulate interest if the borrower is unemployed when the investments are financed by such loans the interest payments are regarded as a negative part of the surplus the agents bargain over as a result a worker pays the same share of the interest as he receives of the return

efficiency of simultaneous search this paper presents an equilibrium labor search model in which workers can simultaneously apply to multiple firms to increase their search intensity they observe firms wage postings before choosing where to apply owing to coordination frictions a firm may not receive any applications otherwise it is able to hire unless all its applicants have better offers it is shown that the equilibrium converges to the efficient walrasian outcome as application costs vanish even for nonnegligible application costs the entry of firms the search intensity and the number of filled vacancies are constrained efficient wage dispersion is essential for constrained efficiency

efficiency of investment in human and physical capital in a model of bilateral search and bargaining a matching model is used to analyze the effect of search frictions on incentives to invest in human and physical capital equilibrium involves inefficient low levels of investment the source of the inefficiency cannot be attributed solely to either search or bargaining schemes that assist matching are pareto improving while the ratio of workers to firms remains fixed intermediaries that pay owners according to the amount of capital carried into the market are able to generate efficient outcomes such intervention may not eliminate inefficiencies when the ratio is endogenized policy implications include encouragement of investment even while abstracting from growth this paper examines investment in human and physical capital in an environment with explicit frictions in particular i analyze a random matching model where workers must search for employers and vice versa but one that is generalized beyond the previous literature to include ex ante investments on both sides of the market 2 the model generates equilibria with inefficiently low levels of investment to identify the source of the inefficiency its robustness to variations in the environment is considered i also analyze a generalized version of the model in which individuals can choose whether to invest in physical or human capital i e whether to become employers or workers the model predicts that the

holdups and efficiency with search frictions a natural holdup problem arises in a market with search frictions firms have to make a range of investments before finding their employees and larger investments translate into higher wages in particular when wages are determined by ex post bargaining the equilibrium is always inefficient recognizing that capital intensive production relations have to pay higher wages firms reduce their investments this can only be prevented by removing all the bargaining power from the workers but this in turn depresses wages below their social product and creates excessive entry of firms in contrast to this benchmark we show that efficiency is achieved when firms post wages and workers can direct their search toward more attractive offers this efficiency result generalizes to an environment with imperfect information where workers only observe a few of the equilibrium wage offers we show that the underlying reason for efficiency is not wage posting per se but the ability of workers to direct their search toward more capital intensive jobs

human capital investment with competitive labor search abstract we study human capital accumulation in the presence of labor search frictions given that unemployed workers can default on their education loans skilled individuals with a larger debt burden prefer riskier but better paid careers than is socially desirable a higher level of employment risk in turn depresses the skill premium and the incentives to invest in education the equilibrium allocation is characterized by too low employment underinvestment by the poor and too little investment in skill intensive technologies a public education system funded by graduate taxes can restore efficiency and it would also reduce wage inequality

optimal policies for inventory systems with lateral transshipments using lateral transshipments can be beneficial in order to improve service levels and to reduce system costs this paper deals with a single echelon inventory system with two identical locations demands are generated by stationary and independent poisson processes in general if a demand occurs at a location and there is no stock on hand the demand is assumed to be backordered or lost however in this paper lateral transshipments serve as an emergency supply in case of stock out in this paper the rule for lateral transshipments is given while the ordering policies for normal replenishments are optimized the transshipment rule is to always transship when there is a shortage at one location and stock on hand at the other first we assume that the locations apply r q policies for normal replenishments and show that the optimal policies are not necessarily symmetric even though the locations are identical this means that one cannot in general assume that the optimal policy is symmetric under symmetric assumptions second we relax the assumption of r q policies and derive the optimal replenishment policy using stochastic dynamic programming

skills search and the persistence of high unemployment abstract the persistence of high unemployment rates in europe has fueled theories advocating the existence of multiple natural rates of unemployment labor market institutions and increasing returns to scale have been singled out as the main causes of multiplicity and therefore of high unemployment traps the contribution of this paper is both to expand the set of mechanisms leading to multiple natural rates of unemployment and to establish a minimum set of assumptions under which such multiplicity may arise to this aim a search matching model is presented where households allocate time to market and non market activities and invest both in physical and human capital it is shown that under the standard assumption of concavity in production and matching such a model yields multiple long run equilibria with different rates of unemployment this result does not rely on labor market institutions or increasing returns to scale multiplicity in our model arises from differences in the intensity of use of human capital across time consuming activities

cost parametric analysis of lateral transshipment policies in two echelon supply chains abstract in this paper we examine the cost effects of two lateral intra echelon transshipment approaches in a two echelon supply chain network with a single supply source at the higher echelon and multiple retail locations at the lower through a series of simulation experiments under different operating conditions an important finding is that either of the proposed lateral shipment approaches is considerably superior to a policy of no such shipments albeit at the expense of increased transportation activity further an ad hoc emergency transshipment approach appears to be significantly more effective in terms of several important criteria as compared to a more systematic transshipment technique based on stock level equalization

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