urban spatial structure urban structure is increasingly characterized by decentralization dispersion and multiple employment centers much is known empirically about such patterns and about how the interplay between agglomerative and dispersive forces generates spatial structures that are complex and prone to multiple equilibria and dynamic path dependence these forces operate at different spatial scales many entail unpriced interaction and external scale economies deriving from product differentiation and endogenous technical change appear particularly important because these forces interact in complex ways inefficiencies in urban structure are resistant to simple policy interventions

human capital inequality and economic growth some new evidence this paper provides new measures of human capital inequality for a broad panel of countries taking attainment levels from barro and lee 2001 we compute gini coefficients and the distribution of education by quintiles for 108 countries over five year intervals from 1960 to 2000 using this new cross country data on human capital inequality two main conclusions are obtained first most countries in the world have tended to reduce the inequality in human capital distribution second human capital inequality measures provide more robust results than income inequality measures in the estimation of standard growth and investment equations

a welfare measure of offset effects in health insurance abstract changing health insurance coverage for one service may affect use of other insured services when improving coverage for one service reduces use of another the savings are referred to as offset effects for example costs of better coverage for prescription drugs may be partly offset by reductions in hospital costs offset effects have welfare implications but it has not been clear how to value these impacts in design of health insurance we show that plan paid rather than total spending is the right welfare measure of the offset effect and go on to develop a sufficient statistic for evaluating the welfare effects of change in coverage in the presence of multiple goods we derive a simple rule for when a coverage improvement increases welfare due to offset effects

estimating the lead time demand distribution when the daily demand is non normal and autocorrelated hon shiang lau abstract this paper develops convenient formulas for estimating the probability distribution of lead time demand when the inventory item s daily demand follows a probability distribution of any arbitrary shape and when simple univariate models can be found for the autocorrelated daily demand series numerical examples are presented to illustrate the use of these formulas the numerical results also indicate that significant error may be incurred when inventory decisions are made without proper consideration of the autocorrelations or the arbitrary distribution shapes of daily demands

on the causal links between fdi and growth in developing countries we analyse the granger causal relationships between foreign direct investment fdi and gdp in a sample of 31 developing countries covering 31 years using estimators for heterogeneous panel data we find bi directional causality between the fdi to gdp ratio and the level of gdp fdi has a lasting impact on gdp while gdp has no longrun impact on the fdi to gdp ratio in that sense fdi causes growth furthermore in a model for gdp and fdi as a fraction of gross capital formation gcf we also find long run effects from fdi to gdp this finding may be interpreted as evidence in favour of the hypotheses that fdi has an impact on gdp via knowledge transfers and adoption of new technology

integrating replenishment decisions with advance demand information there is a growing consensus that a portfolio of customers with different demand lead times can lead to higher more regular revenues and better capacity utilization customers with positive demand lead times place orders in advance of their needs resulting inadvance demand information this gives rise to the problem of finding effective inventory control policies under advance demand information we show that state dependent s s and base stock policies are optimal for stochastic inventory systems with and without fixed costs the state of the system reflects our knowledge of advance demand information we also determine conditions under which advance demand information has no operational value a numerical study allows us to obtain additional insights and to evaluate strategies to induce advance demand information

decomposing learning by doing in new plants the paper examines learning by doing in the context of a production function in which the other arguments are labor human capital physical capital and vintage as a proxy for embodied technical c

banking the poor via savings accounts evidence from a field experiment abstract in a setting with low penetration of bank accounts i randomly gave access to bank accounts with zero fees at local bank branches to a large sample of female household heads in nepal the zero fees and physical proximity of the bank led to high take up and usage rates compared to similar studies in other settings however impact on income aggregate expenditures and assets are too imprecisely estimated to draw a conclusion i do find reallocation of expenditures across categories e g more spending on education and meat and fish and less on health and dowries and higher ability to cope with shocks on qualitative outcomes i find households report that their overall financial situation has improved the lack of a clear story on mechanisms yet strong result on aggregate self perception of financial wellbeing is consistent with access to quality savings accounts leading to household improvements via multiple mechanisms

optimal policies and approximations for a serial multiechelon inventory system with time correlated demand since clark and scarf s pioneering work most advances in multiechelon inventory systems have been based on demand processes that are time independent this paper revisits the serial multiechelon inventory system of clark and scarf and develops three key results first we provide a simple lower bound approximation to the optimal echelon inventory levels and an upper bound to the total system cost for the basic model of clark and scarf second we show that the structure of the optimal stocking policy of clark and scarf holds under time correlated demand processes using a martingale model of forecast evolution third we extend the approximation to the time correlated demand process and study in particular for an autoregressive demand model the impact of lead times and autocorrelation on the performance of the serial inventory system

a time series framework for supply chain inventory management we consider a supply chain in which the underlying demand process can be described in a linear state space form inventory is managed at various points of the chain members based on local information that each member observes and continuously updates the key feature of our model is that it takes into account the ability of the members to observe subsets of the underlying state vector and adopt their forecasting and replenishment policies accordingly this enables us to model situations in which the members are privy to certain explanatory variables of the demand with the latter possibly evolving according to a vector autoregressive time series for each member we identify an associated demand evolution model for which we propose an adaptive inventory replenishment policy that utilizes the kalman filter technique we then provide a simple methodology for assessing the benefits of various types of information sharing agreements between members of the supply chain we also discuss inventory positioning and cost performance assessment in the supply chain our performance metrics and inventory target levels are usually presented in matrix forms allowing them to accommodate a relatively large spectrum of linear demand models and making them simple to implement several illustrations for possible applications of our models are provided

environment health and human capital in this review we discuss three major contributions economists have made to our understanding of the relationship between the environment and individual well being first in explicitly recognizing how optimizing behavior particularly in the form of residential sorting can lead to nonrandom assignment of pollution economists have employed a wide range of quasi experimental techniques to develop causal estimates of the effect of pollution second economic research has placed a considerable focus on the role of avoidance behavior which is an important component for understanding the difference between biological and behavioral effects of pollution and for proper welfare calculations lastly economic research has expanded the focus of analysis beyond traditional health outcomes to include measures of human capital including labor supply productivity and cognition our review of the quasi experimental evidence on this topic suggests that pollution does indeed have a wide range of effects on individual well being even at levels well below current regulatory standards given the importance of health and human capital as an engine for economic growth these findings underscore the role of environmental conditions as an important factor of production jel i12 i31 j24 q51 q53

a single item inventory model for expected inventory order crossovers abstract expected inventory order crossovers occur if at the moment of ordering it is expected that orders will not arrive in the sequence they are ordered recent research has shown that a expected inventory order crossovers will be encountered more frequently in future and that b use of a myopic order up to policy based on a stochastic dynamic programming approach leads to improved performance compared to the classical approach in this paper we show that the improved policy is still heuristic in nature as it neglects several control options that are available on the various ordering moments and makes some restrictive assumptions with respect to the separability i e decomposability of the stochastic dynamic programming problem we propose further improvements in the policy for situations where a quadratic cost function is appropriate

note the newsvendor model with endogenous demand this paper considers a firm s price and inventory policy when it faces uncertain demand that depends on both price and inventory level the authors extend the classic newsvendor model by assuming that expected utility maximizing consumers choose between visiting the firm and consuming an exogenous outside option the outside option represents the utility the consumer forgoes when she chooses to visit the firm before knowing whether or not the product will be available the authors investigate both the case in which the firm s price is exogenous and the case in which price is chosen optimally the paper makes two contributions first the authors show that the firm holds more inventories provides a higher fill rate attracts more customers and earns higher profits when it internalizes the effect of its inventory on demand second the authors show that in the endogenous price case the firm s two dimensional decision problem can be reduced to two sequential single variable optimizations as a result the endogenous price case is as easy to solve as the exogenous price case

the impact of new drugs on us longevity and medical expenditure 1990 2003 evidence from longitudinal disease level data a number of econometric studies charles r hulten 1992 byong hong bahk and michael gort 1993 plutarchos sakellaris and daniel j wilson 2004 have investigated the hypothesis that capital equipment employed by us manufacturing firms embodies technological change i e that each successive vintage of investment is more productive than the last equipment is expected to embody significant technical progress due to the relatively high research and development r d intensity of equipment manufacturers the method that has been used to test the equipment embodied technical change hypothesis is to estimate manufacturing production functions including mean vintage of equipment as well as quantities of capital and labor these studies have concluded that technical progress embodied in equipment is a major source of manufacturing productivity growth embodied technical progress may also be an important source of economic growth in healthcare one important input in the production of health pharmaceuticals is even more r d intensive than equipment according to the national science foundation nsf the r d intensity of drugs and medicine manufacturing is 74 percent higher than the r d intensity of machinery and equipment manufacturing therefore it is quite plausible that there is also a high rate of pharmaceutical embodied technical progress this study examines the effect of changes in the vintage distribution of prescription drugs on us longevity and medical expenditure during the 1990 2003 period we will estimate the following model using longitudinal disease level data

broadband penetration and economic growth nexus evidence from cross country panel data this article investigates whether there are granger causal relationships between broadband penetration degree of urbanization foreign direct investment and economic growth using a panel data set covering the g 20 countries for the period 1998 2011 using our multivariate framework we first find that all of the variables are cointegrated our findings further reveal a network of causal connections between the variables including short run bidirectional causality between broadband penetration and economic growth among the more developed countries within the g 20 on the other hand for the developing countries within the g 20 there is evidence of unidirectional causality from economic growth to broadband penetration

a periodic review model with serially correlated inventory level dependent demand abstract it has been established that the demand rates of many consumer products are serially correlated and are dependent on the amount of inventory displayed to the customer a periodic review model is developed that considers both of these effects an adaptive base stock policy based on the critical fractile is presented and a solution methodology is developed the effect of this demand pattern on the safety stock requirement is investigated

does human capital matter for growth in oecd countries a pooled mean group approach abstract unlike previous panel data studies using an improved dataset and pmg estimators we find a significant impact of human capital on growth the estimated long run elasticity of output to human capital is consistent with the microeconomic evidence on returns to schooling

some insights regarding the optimal reorder period in periodic review inventory systems abstract the periodic review inventory system is not only pervasive but also has an extensive literature dealing with various aspects from its theoretical underpinnings through to its performance however the selection of the best review period and its behaviour with respect to basic inventory parameters such as demand and supply variability appears to be poorly understood in this paper we treat the normal and gamma distributions which are probably the two most commonly used distributions of demand over the key protection time interval in a periodic review system we show that the total cost function is not necessarily well behaved as a function of the review period in particular it can be non convex which complicates the determination of the best value of the review interval also we demonstrate and explain how the best review period changes as the values of various parameters are modified some of these changes are initially counterintuitive in nature managerially oriented interpretations should also be helpful to organisations seeking improvement in inventory system performance

management of a periodic review inventory system using bayesian model averaging when new marketing efforts are made abstract many companies invest in various marketing efforts such as price promotion and advertising in order to attract new customers and build customer loyalty this paper examines the problem of setting efficient inventory levels when new marketing efforts are made and product demand is autocorrelated we assume that the inventory manager operates with a base stock policy based on a critical fractile if marketing has a temporary effect the underlying demand tends to revert to a long term equilibrium trend and the inventory manager needs to use a stationary demand model e g autoregressive model to determine the required inventory level in contrast if the effect is permanent demand shocks contain an element that represents a permanent departure from previous levels and a non stationary demand model e g random walk needs to be used instead we show that the required inventory behaves much differently for the case of using a stationary demand model as opposed to a non stationary model but it is difficult in practice to identify a correct demand model in the absence of a long sampling span in this paper we propose an inventory model that explicitly acknowledges uncertainty over stationary and non stationary demand models in response to new marketing efforts the proposed model averages the inventory policies of the two demand models weighted by each model s posterior probability this is an extension of bayesian model averaging simulation results demonstrate that the bayesian model averaging inventory model improves the inventory system

bayes solution to dynamic inventory models under unknown demand distribution this paper considers the periodic review inventory problem for which one or more parameters of the demand distribution are unknown with a known prior distribution chosen from the natural conjugate

human capital and growth abstract this paper describes a growth model with the property that human capital accumulation can account for all observed growth the model is shown to be consistent with evidence on individual productivities as measured by census earnings data the central hypothesis is that we learn more when we interact with more productive people

what do we know about economic growth or why don t we know very much summary the last 10 years has seen an explosion in cross country econometric studies of growth driven by two factors new mathematical models of the growth process that lend themselves to econometric testing and new data sets that make such testing possible this paper looks at a selective review of these studies it concludes that the results are disappointing in that no model has proven robust to trial by repeated regression the paper suggests some reasons for this including that the tested models tend to be ahistorical and over simple in terms of their causal accounts it concludes with possible lessons for econometric work in this area 2000 elsevier science ltd all rights reserved

interindustry variation in the costs of job displacement job displacement entails a substantial wage reduction for most displaced workers we show that the mean reduction the tenure profile of reductions and the experience profile of reductions all vary substantially across industries we then link this interindustry variation to analogous variation in firm size unionization wage levels and the incidence of employer provided training while these industry characteristics explain some of the interindustry variation in mean wage reductions they do not explain variation in the tenure or experience profiles of wage reductions

value of information in capacitated supply chains we incorporate information flow between a supplier and a retailer in a two echelon model that captures the capacitated setting of a typical supply chain we consider three situations 1 a traditional model where there is no information to the supplier prior to a demand to him except for past data 2 the supplier knows the s s policy used by the retailer as well as the end item demand distribution and 3 the supplier has full information about the state of the retailer order up to policies continue to be optimal for models with information flow for the finite horizon the infinite horizon discounted and the infinite horizon average cost cases study of these three models enables us to understand the relationships between capacity inventory and information at the supplier level as well as how they are affected by the retailer s s s values and end item demand distribution we estimate the savings at the supplier due to information flow and study when information is most beneficial

inventory control in a fluctuating demand environment we present an inventory model where the demand rate varies with an underlying state of the world variable this variable can represent economic fluctuations or stages in the product life cycle for example we derive some basic characteristics of optimal policies and develop algorithms for computing them in addition we show that certain monotonicity patterns in the problem data are reflected in the optimal policies

information distortion in a supply chain the bullwhip effect this article originally appeared in management science april 1997 volume 43 number 4 pp 546 558 published by the institute of management sciences consider a series of companies in a supply chain each of whom orders from its immediate upstream member in this setting inbound orders from a downstream member serve as a valuable informational input to upstream production and inventory decisions this paper claims that the information transferred in the form of orders tends to be distorted and can misguide upstream members in their inventory and production decisions in particular the variance of orders may be larger than that of sales and distortion tends to increase as one moves upstream a phenomenon termed bullwhip effect this paper analyzes four sources of the bullwhip effect demand signal processing rationing game order batching and price variations actions that can be taken to mitigate the detrimental impact of this distortion are also discussed

an inventory model with deteriorating items under inflation when a delay in payment is permissible abstract this study develops an inventory model for initial stock dependent consumption rate when a delay in payment is permissible in the inventory model shortages are not allowed the effect of the inflation rate deterioration rate initial stock dependent consumption rate and delay in payment are discussed in the study mathematical models are also derived under two different circumstances i e case i the credit period is less than or equal to the cycle time for settling the account and case ii the credit period is greater than the cycle time for settling the account besides expressions for an inventory system s total cost are derived for these two cases moreover a computational procedure and gino lasdon et al acm transactions mathematical software 4 1978 34 50 are proposed to obtain the optimal order size and cycle time the results can help managers determine the optimal total cost finally a numerical example demonstrates the applicability of the proposed model

scarf s state reduction method flexibility and a dependent demand inventory model we consider a finite horizon inventory model with linear holding shortage and ordering costs the demand random variables are dependent and average demand is described by an exponential smoothing formula this model can be formulated as a two state variable inventory level weighted past demands dynamic program using a procedure first developed by scarf for a bayesian inventory model we are able to reformulate the model as a one state variable dynamic program resulting in a considerable computational saving over the two state variable formulation we also show that this dependent demand model orders less than or equal the amount ordered by a comparable independent demand model we establish this result under the assumption that demand represents failures that are repaired by the beginning of the next period

does human capital constrain the impact of foreign direct investment and remittances on economic growth in ghana this article empirically investigates whether human capital constrains the impact of foreign direct investment fdi and remittances on economic growth in ghana an economic growth model for ghana is specified and estimated using fully modified ordinary least squares fmols estimator and employing annual data spanning the period 1965 to 2008 empirical results indicate that fdi and remittances are key determinants of economic growth in ghana results indicate that human capital enhances the impact of fdi and remittances on economic growth although both government expenditure and trade openness are growth enhancing government expenditure appears to crowd out private investment empirical results also indicate that domestic inflationary pressures unstable political environment and volatile global economy exert a negative impact on economic growth in ghana

where has all the education gone cross national data show no association between increases in human capital attributable to the rising educational attainment of the labor force and the rate of growth of output per worker this implies that the association of educational capital growth with conventional measures of total factor production is large strongly statistically significant and negative these are on average results derived from imposing a constant coefficient however the development impact of education varied widely across countries and has fallen short of expectations for three possible reasons first the institutional governance environment could have been sufficiently perverse that the accumulation of educational capital lowered economic growth second marginal returns to education could have fallen rapidly as the supply of educated labor expanded while demand remained stagnant third educational quality could have been so low that years of schooling created no human capital the extent and mix of these three phenomena vary from country to country in explaining the actual economic impact of education or the lack thereof

economic growth as a function of human capital internet and work the world bank has suggested the need to enhance information and communication technology skills in all sectors because a 10 increase in internet connectivity was found to boost gdp growth by 1 38 simultaneously the oecd argued that high internet access rates generate a 2 increase in gdp because the internet positively affects economic growth we investigated the relationship between an economically active population human capital and technology to evaluate these effects in mexico a data series from 1991 to 2010 was analysed in three stages according to the least squares method a cobb douglas function under the solow model was considered technology and internet access were found to positively affect top level students and graduate students and thus contribute to the global innovation index

managing inventory with the prospect of obsolescence how should inventory management respond when there is a possibility of imminent obsolescence or more generally deteriorating demand we use an inventory control model to address this question the model incorporates a markovian submodel to describe the uncertain events leading to obsolescence these events and their uncertainties come in a variety of patterns we devote considerable attention to specifying the submodel and we compare a few alternatives numerically also we compare optimal policies to simpler alternatives and we investigate the response of the model to parameter changes generally we find that obsolescence does or should have a substantial impact in the way inventories are managed the nature of these effects moreover is fairly intricate it appears that obsolescence cannot be captured in a simpler model through parameter adjustments these conclusions presume that we cannot dispose of excess stock either directly or through price promotions we show also that the disposal option can make the problems of obsolescence more manageable

a model for optimizing retail space allocations the allocation of scarce shelf space among competing products is a central problem in retailing space allocation affects store profitability through both the demand function where both main and cross space elasticities have to be considered and through the cost function procurement carrying and out of stock costs a model is developed which uniquely incorporates both effects a case study is used to estimate the parameters and the problem is solved within a geometrical programming framework an extensive comparison with alternative procedures suggests this general model leads to significantly different allocation rules and superior profit performance

inventories and the volatility of production a stylized fact associated with inventory behavior is that the variance of production exceeds the variance of sales this paper presents a model of production decisions with demand uncertainty that incorporates no nnegativity constraints on inventories even with no productivity shocks optimal behavior by the firm is consistent with this stylized fact either if demand exhibits positive serial correlation or if the firm can backlog excess demand the reason is that a demand shock affects both the actual inventory level given unchanged production and the desired level production must replenish the stock and adjust to the new desired level copyright 1987 by american economic association

safety stock determination with correlated demands and arbitrary lead times abstract in this new paper a new method is proposed for determining the safety stock when daily demands are autocorrelated and lead times follow an arbitrary distribution the method is then used as a basis for examining effects on the safety stock when the usual assumptions namely independence and normality of daily demand and normality of lead times are violated the new method is derived by using inequalities on the basis of probability arguments it is simple to use and provides an upper bound of the safety stock further numerical investigation based on the new method shows that the effect of autocorrelation is more pronounced than departure from normality in determining the safety stock substantial error may be incurred if such autocorrelation is ignored in the test cases

trivariate causality between economic growth urbanisation and electricity consumption in angola cointegration and causality analysis abstract this paper investigates the causal relationship between economic growth urbanisation and electricity consumption in the case of angola while utilizing the data over the period of 1971 2009 we have applied lee and strazicich 2003 the review of economics and statistics 63 1082 1089 2004 working paper department of economics appalachian state university unit root tests to examine the stationarity properties of the series using the gregory hansen structural break cointegration procedure as a complement we employ the ardl bounds test to investigate long run relationships the vecm granger causality test is subsequently used to examine the direction of causality between economic growth urbanisation and electricity consumption our results indicate the existence of long run relationships we further observe evidence in favour of bidirectional causality between electricity consumption and economic growth the feedback hypothesis is also found between urbanisation and economic growth urbanisation and electricity consumption granger cause each other we conclude that angola is energy dependent country consequently the relevant authorities should boost electricity production as one of the means of achieving sustainable economic development in the long run

financial depth internet penetration rates and economic growth country panel evidence abstractthe article investigates causal relationships between internet penetration rates financial depth and per capita economic growth in the next 11 countries using panel vector autoregressive var approaches our empirical results show that these variables are cointegrated moreover we find bidirectional causality between internet penetration rates and economic growth and between financial depth and economic growth in the short run

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

urban concentration agglomeration economies and the level of economic development there is a view among planners in the developing nations that the process of economic development invariably results in the concentration of population in one or two primal cities there is also however considerable disagreement over whether this apparent relationship is either necessary or desirable proponents on the one hand argue that concentrated urbanization strongly supports industrial development through the realization of scale and agglomeration economies 2 dissenters from this view feel that urban concentration creates serious social costs and results more from historical or political forces than economic ones in this case policies aimed at decentralizing growth can achieve social objectives without sacrificing economic efficiency despite these deliberations it is surprising that there has been little or no empirical study of urban concentration on either a longitudinal or cross national basis the major related work which exists is williamson s research on economic development and income inequality 3 williamson demonstrates that as economic growth begins inequality initially increases but then diminishes in the more advanced stages of development this coincides with hirschman s4 view that industrialization eventually spreads into more backward areas reduc

myopic policies for some inventory models with uncertain demand distributions the majority of papers on stochastic inventory theory make the assumption that the distribution of consumer demand in each time period is known with certainty while this assumption is unsupported in many applied contexts it is conventionally held that more realistic models are more difficult to solve and will not yield simple operational policies this paper shows that a simple inventory policy based upon a critical fractile can be optimal or near optimal in some inventory models with parameter adaptive demand processes in these some parameter of the demand distribution is not known with certainty and estimates of the parameter are updated in a statistical fashion as demand is observed through time examples include exponentially smoothed forecasts and bayesian updating of parameter estimates bounds on the value loss relative to optimal cost when using the critical fractile policy can be calculated directly from the problem data some numerical examples illustrate the technique

the human capital and economic growth nexus in east and south asia abstractthis study adopts a disaggregated regional focus to test for the human capital hc growth nexus in selected nine asian countries it utilizes the empirical bayesian methodology which addresses not only the heterogeneity issue but it also utilizes the common structural priors of regional countries to yield informationally efficient estimates of the impact of hc on the stock and levels of gdp various measures of hc are utilized to determine which of these produces a better explanation of economic growth in the two asian regions the study finds that primary and secondary education was more prominent in explaining the fluctuations of economic growth in east asia whereas tertiary and vocational education showed positive effects on economic growth in south asia government expenditures on education were also found to positively affect economic growth in both regions the results shed new evidence to establish that the differences in growth rates within east and south asia are associated with diffe

growth accounting when technical change is embodied in capital this paper revisits the hypothesis that technical change is embodied in capital it extends old results to make them more relevant to the contemporary debates about the adjustment of investment goods for quality change and about the role of embodied technical change as a source of economic growth it is shown that the failure to adjust capital for quality change has the effect of suppressing the quality effects into the conventional total factor productivity residual and it is found that approximately 20 percent of the residual growth of quality adjusted output could be attributed to embodied technical change copyright 1992 by american economic association