the empirical content of the roy model this paper clarifies and extends the classical roy model of self selection and earnings inequality the original roy model based on the assumption that log skills are normally distributed is shown to imply that pursuit of comparative advantage in a free market reduces earnings inequality compared to the earnings distribution that would result if workers were randomly assigned to sectors aggregate log earnings are right skewed even if one sectoral distribution is left skewed most major implications of the log normal roy model survive if differences in skills are log concave however few implications of the model survive if skills are generated from more general distributions we consider the identifiability of the roy model from data on earnings distributions the normal theory version is identifiable without regressors or exclusion restrictions sectoral distributions can be identified knowing only the aggregate earnings distribution for general skill distributions the model is not identified and has no empirical content with sufficient price variation the model can be identified from multimarket data cross sectional variation in regressors can substitute for price variation in restoring empirical content to the roy model

international trade and labor market discrimination textabstractwe embed a competitive search model with labor market discrimination or nepotism into a two sector two country framework in order to analyze how labor market discrimination impacts the pattern of international trade and also how trade trade affects discrimination discrimination or nepotism reduces the matching probability and output in the skilled labor intensive differentiated product sector so that the country with more discriminatory firms has a comparative advantage in the simple sector as countries alter their production mix in accordance with their comparative advantage trade liberalization can then reinforce the negative effect of discrimination on development in the more discriminatory country and reduce its effect in the country with fewer discriminatory firms similarly the profit difference between non discriminatory and discriminatory firms increases in the less discriminatory country and shrinks in the more discriminatory one in this way trade can further reduce discrimination in a country where it is less prevalent and increase it where it is more firmly entrenched

racial discrimination in the labor market theory and empirics we review theories of race discrimination in the labor market taste based models can generate wage and unemployment duration differentials when combined with either random or directed search even when strong prejudice is not widespread but no existing model explains the unemployment rate differential models of statistical discrimination based on differential observability of productivity across races can explain the pattern and magnitudes of wage differentials but do not address employment and unemployment at their current state of development models of statistical discrimination based on rational stereotypes have little empirical content it is plausible that models combining elements of the search models with statistical discrimination could fit the data we suggest possible avenues to be pursued and comment briefly on the implication of existing theory for public policy jel j15 j31 j64 j71

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

discrimination in an equilibrium search model i construct an equilibrium search model where some employers have a distaste for hiring minority workers and show that this bias results in economic discrimination against minority workers although only unprejudiced firms hire minority workers minority workers receive lower wages than workers not facing discrimination whenever any employers in the market have a distaste for minority workers one implication of the model is that gender or racial wage differentials understate the utility loss from discrimination in addition the wages of minority workers increase when their proportion increases in the labor market

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

the trend in the male female wage gap in the united states despite the rise in the feminist movement the enactment of equal opportunity legislation and the rapid increase in women s labor force participation a substantial sex differential in wages has persisted in the united states for at least 4 decades measured by hourly earnings of year round workers this wage gap was 31 in 1955 widened to a 35 37 range by the 1960s and early 1970s and then narrowed to 33 by 1982 this paper examines the extent to which changes in the characteristics of men and women in the labor force and other factors can account for the observed pattern the main finding is that increases in women s labor force participation were initially associated with a declining skill level of employed women relative to employed men where skill is measured by years of schooling and job tenure more recently the work experience of employed women has been increasing which helps account for the recent narrowing trend in the wage gap during the 1970s the wage gap probably woul have narrowed m

racial disparity in unemployment abstract in the united states black workers earn less than their white counterparts and have higher rates of unemployment empirical work indicates that most of this wage gap is accounted for by differences in cognitive skills that emerge at an early age in this paper we demonstrate that the same is not true for black white disparity in unemployment a large unexplained unemployment differential motivates the paper s second contribution a potential theoretical explanation this explanation is built around a model that embeds statistical discrimination into the subjective worker evaluation process that lies at the root of the efficiency wage theory of equilibrium unemployment

multi product lot sizing with a transportation capacity reservation contract abstract although transportation costs can form more than 50 of the total logistics costs of a product they are often neglected in lot sizing research and modelling nonetheless the body of research that does take transportation costs into account is gradually growing the bulk of this type of research however assumes that freight rates decrease as shipping weights and or volumes increase inspired by the situation with a large european manufacturing company we study a multi product lot sizing model where in any period any portion of a reserved transportation capacity can be used in exchange for a guaranteed price if the capacity is insufficient then the shipper needs to contract additional transportation capacity on the spot market where the prevailing price is higher accordingly the freight rates are piece wise linearly increasing in our model we prove that the problem of determining transportation lot sizes so as to meet warehouse demand with no backlogging allowed and to minimize total costs that is the sum of inventory carrying ordering and transportation costs is np hard in the strong sense furthermore we present a lagrangean relaxation algorithm to compute lower and upper bounds of which comprehensive computational experiments show the compelling performance in terms of quality and speed

informal job search and black youth unemployment in this paper i analyze how young black and white unemployed jobseekers use various methods of search and the employment outcomes which result from their use the focus is on distinguishing informal search methods i e friends and relatives or direct application without referral from more formal ones in analyzing racial differences the results show that the two informal methods of search account for about 90 of the difference in employment probabilities between white and black youth this also accounts for 57 71 of the difference in unemployment rates between the two furthermore most of these results reflect differences in the ability of these methods to generate job offers as opposed to differences in search effort or job acceptance rates however our ability to explain these differences through personal family and household characteristics was generally quite limited this abstract was borrowed from another version of this item

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

job discrimination market forces and the invisibility hypothesis the invisibility hypothesis holds that the job skills of disadvantaged workers are not easily discovered by potential new employers but that promotion enhances visibility and alleviates this problem then at a competitive labor market equilibrium firms profit by hiding talented disadvantaged workers in low level jobs consequently those workers are paid less on average and promoted less often than others with the same education and ability as a result of the inefficient and discriminatory wage and promotion policies disadvantaged workers experience lower returns to investments in human capital than other workers

pay differences among the highly paid the male female earnings gap in lawyers salaries this article uses very detailed information on graduates of the university of michigan law school to examine male female pay differences in that population men and women in this population have virtually identical human capital on graduation from law school allowing us to examine carefully the different impact of children and work history on men s and women s careers and earnings taking time from work in order to care for children reduces wages significantly but a rich set of controls including childcare work history school performance and job setting measures still leave one fourth to one third of the earnings gap unexplained

directed search coordination failure and seller profits an experimental comparison of posted pricing with single and multiple prices we experimentally examine posted pricing and directed search in one treatment capacity constrained sellers post fixed prices which buyers observe before choosing whom to visit in the other firms post both single buyer applied when one buyer visits and multibuyer when multiple buyers visit prices we find based on a 2 2 two buyers and two sellers market and a follow up experiment with 3 and 2 3 markets that multibuyer prices can be lower than single buyer prices or prices in the one price treatment also allowing the multibuyer price does not affect seller profits and increases market frictions

the swings of u s inflation and the gibson paradox in recent business cycles u s inflation has experienced a reduction of volatility and a severe weakening in the correlation to the nominal interest rate gibson paradox we examine these facts in an estimated dynamic stochastic general equilibrium model with money our findings point at a flatter new keynesian phillips curve higher price stickiness and a lower persistence of markup shocks as the main explanatory factors in addition a higher interest rate elasticity of money demand an increasing role of demand side shocks and a less systematic behavior of fed s monetary policy also account for the recent patterns of u s inflation dynamics jel e32 e47

reservation wages and their labor market effects for black and white male youth this paper presents an empirical analysis of self reported reservation wages for unemployed young black and white males the results show that young blacks seek wages which are comparable to those of young whites in absolute terms but which are higher relative to what is available on the demand side of the market these relatively higher reservation wages of young blacks contribute to their unemployment durations and somewhat to their subsequently received wages changes in reservation wages may thus help to explain the trends in wages and employment of young blacks in recent years

wage differentials discrimination and efficiency abstract i analyze a large labor market where homogeneous firms post wages to direct the search of workers who differ in productivity i show that the model has a unique equilibrium the wage differential depends positively on the workers productivity differential only when the latter is large when the productivity differential is small high productivity workers get a lower wage than low productivity workers this reverse wage differential remains even when the productivity differential shrinks to zero however the equilibrium is socially efficient high productivity workers always get the employment priority and higher expected wages than low productivity workers although discrimination in terms of expected wages does not exist conventional measures are likely to incorrectly find discrimination in the model

the differing nature of black white wage inequality across occupational sectors the nature of racial wage inequality appears to differ across occupation sectors specifically i find that all of the racial wage inequality in the white collar job sector can be accounted for by controlling for the academic skill level of each worker but almost half of the overall racial wage inequality remains in the blue collar sector after controlling for each worker s academic skill relatedly after controlling for academic skill i find that black workers are actually more likely to work in the white collar sector than white workers i show that these findings are consistent and arguably directly implied by both preference based and statistical based models of discrimination however omitted variable bias and measurement error also cannot be ruled out as possible explanations

heterogeneous firms and the organization of production firms in the same industry exhibit systematic differences in the organization of production and the structure of employment entrepreneurial ability is the specific scarce input that limits the size of a firm this input must be allocated to two activities coordinating production and monitoring workers able entrepreneurs can convert calendar time into larger supplies of coordinating effort that enable them to assemble large firms greater ability implies a higher shadow price of time which increases the implicit costs of monitoring a dispersion of entrepreneurial abilities generates an equilibrium size distribution of firms differences in monitoring costs affect the choice of worker productivities the design of products and the organization of production the monitoring cost hypothesis advanced in this paper goes a long way in explaining the equilibrium of an industry containing heterogeneous firms that differ in size and behavior

labor turnover wage structures and moral hazard the inefficiency of competitive markets a multiperiod general equilibrium model of the labor market is developed in which risk averse workers are faced with job related uncertainty and labor turnover is costly if a worker is unlucky and suffers a bad job match he quits and joins another firm hoping that he will like its work environment more because the quality of a job match is unobservable workers cannot insure against the risk of a bad match the firm provides implicit insurance against job dissatisfaction typically by paying workers more than their net marginal products in their early years with the firm and less subsequently since the probabilities of the insured against events the quit rates over time are affected by the amount of such insurance provided this implicit insurance is characterized by moral hazard individuals quit when in the absence of insurance they would not the equilibrium contract balances out efficiency in risk bearing with efficiency in turnover incentives we show that the equilibrium contract is not con