forecasting aggregate demand an analytical evaluation of top down versus bottom up forecasting in a production planning framework abstract we study the relative effectiveness of top down td and bottom up bu strategies for forecasting the aggregate demand in a production planning framework the aggregate demand series is composed of several correlated subaggregate components or items each of which is assumed to follow a stationary time series process which is correlated over time as is common in a production planning environment it is assumed that exponential smoothing is used as the forecasting technique under both strategies we analytically show that there is no difference in the relative performance of td and bu forecasting strategies when the time series for all of the subaggregate components follow a first order univariate moving average ma 1 process with identical coefficients of the serial correlation term we then perform a simulation study to examine the case when the coefficients of the serial correlation term for the subaggregate components are not identical it is found from the simulation study that the difference in the performance of the two forecasting strategies is relatively insignificant when the correlation between the subaggregate components is small or moderate

an integrated mixture of local experts model for demand forecasting abstract demand forecasting is an important issue in the supply chain planning process due to its usage for efficiently managing different planning tasks the common techniques adopted to perform such task are easy to use forecasting methods performed in computerised systems with minimum human intervention such as the simple exponential smoothing concerning the drawbacks of these modelling approaches past evidence suggests that they have been less successful in predicting short term fluctuations on demand in this work the simple exponential smoothing method is employed to build an integrated mixture of local experts model imlem for demand forecasting using as independent variable a lagged gross domestic product gdp indicator the imlem is usually employed to deal with rapidly changing situations and it is used in this work to improve the performance of the forecasts by providing a way to take into account short term fluctuations on demand due to changes on economic activity growth within an easy to use forecasting method the proposed method was applied on one step ahead demand forecasting for a brazilian beverage manufacturer for 130 non seasonal stock keeping units skus and the accuracy of the generated forecasts allowed to reduce the forecasting errors the obtained results also supported the decision making process by aiding demand planners concerning how to react to short term fluctuations on demand

regional growth linkages from agriculture pioneering research on downstream linkages from agriculture is said to demonstrate that consumption links rather than production links are the main source of indrect growth effects that these consumption links take the form of labour intensive goods and services produced locally and that the largest farm enterprises are most locally multiplicative of activities mopping up surplus rural labour this article has two purposes first the methodologies assumptions and data base for the quantification of the local and non local regional multiplier effects from agricultural development are examined second the contradictory interpretations for agricultural policy which have arisen from these exercises of quantification are discussed and an attempt made to explain their bases

on the stock control performance of intermittent demand estimators the purpose of this paper is to assess the empirical stock control performance of intermittent demand estimation procedures the forecasting methods considered are the simple moving average single exponential smoothing croston s method and a new method recently developed by the authors of this paper we first discuss the nature of the empirical demand data set 3000 stock keeping units and we specify the stock control model to be used for experimentation purposes performance measures are then selected to report customer service level and stock volume differences the out of sample empirical comparison results demonstrate the superior stock control performance of the new intermittent demand forecasting method and enable insights to be gained into the empirical utility of the other estimators

barriers to participation of the poor in south africa s land redistribution abstract land redistribution is being characterized as poverty alleviation for rural south africa this paper argues that the poor have less inclination to move the distances demanded by the redistribution have less labor available for farming are less able to afford the program s up front costs have fewer farming specific skills and have less capacity to cope with agricultural risk therefore the poor are likely to be rationed out of participation in the program and the land redistribution will have little effect on rural poverty unless demand led targeting is dropped and ancillary programs are employed to make land redistribution attractive for the poor

farm size land yields and the agricultural production function an analysis for fifteen developing countries abstract the paper analyzes the relationship between factor inputs land yields and labor productivity for farms of different size on the basis of fao farm management data for 15 developing countries for all but three countries a strong negative correlation is found between farm size on the one side and factor inputs and yields per hectare on the other the fitting of unconstrained production functions to the above data suggests that in only few cases the decline in yields for increasing farm size can be attributed to decreasing returns to scale the higher yields observed in small farms are mainly to be ascribed to higher factor inputs and to a more intensive use of land therefore where conspicuous labor surpluses exist the superiority of small farming provides solid arguments in favor of land redistribution such an agrarian reform would determine higher output higher labor absorption and a more equitable income distribution thus contributing in a decisive manner to the alleviation of rural poverty the paper also provides estimates of cross sectional production functions for the 15 countries analyzed empirical relations are found between the output elasticities of land labor and intermediate inputs and physical indicators of their scarcity the paper concludes by proposing a simple method for deriving a long term production function for agriculture

the state s role in financing agricultural research abstract recent declines in public agricultural research funding in developing countries may not be as severe or as universal as widely perceived although some research systems are clearly constrained an analysis of the economic characteristics of agricultural research suggests that there may be some crowding out of private finance but the harnessing of additional private resources depends critically on enhancing the profitability and appropriability of research benefits while the case for increasing levels of public funding on research with greater public good characteristics remains strong however the justifiable scrutiny of the state s role in financing agricultural research should not be at the expense of continued efforts to improve the efficiency of agricultural research delivery and the management of existing funds

forecasting and inventory performance in a two stage supply chain with arima 0 1 1 demand theory and empirical analysis the arima 0 1 1 demand model has been analysed extensively by researchers and used widely by forecasting practitioners due to its attractive theoretical properties and empirical evidence in its support however no empirical investigations have been conducted in the academic literature to analyse demand forecasting and inventory performance under such a demand model in this paper we consider a supply chain formed by a manufacturer and a retailer facing an arima 0 1 1 demand process the relationship between the forecasting accuracy and inventory performance is analysed along with an investigation on the potential benefits of forecast information sharing between the retailer and the manufacturer results are obtained analytically but also empirically by means of experimentation with the sales data related to 329 stock keeping units skus from a major european superstore our analysis contributes towards the development of the current state of knowledge in the areas of inventory forecasting and forecast information sharing and offers insights that should be valuable from the practitioner perspective

land reforms poverty reduction and economic growth evidence from india recognition of the importance of institutions that provide security of property rights and relatively equal access to economic resources to a broad cross section of society has renewed interest in the potential of asset redistribution including land reforms empirical analysis of the impact of such policies is however scant and often contradictory this paper uses panel household data from india together with state level variation in the implementation of land reform to address some of the deficiencies of earlier studies the results suggest that land reform had a significant and positive impact on income growth and accumulation of human and physical capital the paper draws policy implications especially from the fact that the observed impact of land reform seems to have declined over time

technical change and labor absorption in asian agriculture some emerging trends abstract increased labor absorption in agriculture has been widely held to be the key to solving unemployment problems in developing asia following the historical experience of east asian countries the new seed fertilizer technology interacting with expansion of irrigation and cropping intensity initially increased labor absorption in wheat and rice production however evidence from recent village studies indicates that new labor saving chemical and mechanical innovations originating in the developed countries are being rapidly adopted by farmers of the developing countries owing to their private cost reducing characteristics this international transfer of technology contributes to increased productivity but results in net reductions of agricultural labor use recognition of the declining capacity of the agricultural sector for labor absorption indicates the need to seek solutions to unemployment problems in the off farm sector

investments in african agricultural research abstract over the past three decades africa s public agricultural research systems have changed in substantive ways the total number of researchers increased fourfold the dependency on expatriate researchers significantly declined while the education levels of national researchers improved initially the growth in research staff was matched by growth in expenditures but since the late 1970s real research spending has stagnated in addition loans and grants from donor agencies now account for a sizeable share of total funding for many african agricultural research systems many of the developments of the past decade in personnel expenditures and sources of support for public sector research and development r d in africa are not sustainable spending per scientist has declined continuously during the past 30 years most dramatically during the 1980s resources are spread increasingly thin over a growing group of researchers which has negative effects on the efficiency and effectiveness of agricultural research in africa

determinants of productivity change using a profit function smallholder agriculture in zimbabwe the concept of total factor productivity tfp the ratio of quality adjusted output to input is straightforward yet explaining pro ductivity change and attributing residual out put growth to its appropriate sources raises numerous problems it has long been argued that technical change policy reform and insti tutional innovation are complements and are all required to achieve sustained productivity growth johnson lipton evenson and kramer binswanger and pingali however in explain ing productivity growth the emphasis usually is put on weather and on investments that gen erate new technology which farmers must be educated to use usually public sector research and development expenditures extension farmer education while these are un doubtedly important the conventional approach see for a survey has often ne glected the role of policies and investments at other stages of the agricultural system affecting farm technology adoption 1the danger of the conventional approach is that it may not adequately measure policy ef fects on productivity through their influence on input and output prices the conventional ap proach may therefore provide misleading impli cations for promoting productivity growth weak infrastructure and institution can prevent

analyzing the welfare improving potential of land in the former homelands of south africa this article contributes to the debate on the role of land in reducing poverty in rural south africa it uses the year of arrival in the former homelands as an instrument for land access and size this identification strategy is based on the fact that african households were forcibly relocated to the homelands during the apartheid due to increasing population pressure later arrivals were less likely to be assigned land the results show that land has a large positive effect on household welfare because the homelands are relatively disadvantaged areas these results provide a lower bound for the positive effects of land on household welfare

performance analysis of demand planning approaches for aggregating forecasting and disaggregating interrelated demands a synchronized and responsive flow of materials information funds processes and services is the goal of supply chain planning demand planning which is the very first step of supply chain planning determines the effectiveness of manufacturing and logistic operations in the chain propagation and magnification of the uncertainty of demand signals through the supply chain referred to as the bullwhip effect is the major cause of ineffective operation plans therefore a flexible and robust supply chain forecasting system is necessary for industrial planners to quickly respond to the volatile demand appropriate demand aggregation and statistical forecasting approaches are known to be effective in managing the demand variability this paper uses the bivariate var 1 time series model as a study vehicle to investigate the effects of aggregating forecasting and disaggregating two interrelated demands through theoretical development and systematic analysis guidelines are provided to select proper demand planning approaches a very important finding of this research is that disaggregation of a forecasted aggregated demand should be employed when the aggregated demand is very predictable through its positive autocorrelation moreover the large positive correlation between demands can enhance the predictability and thus result in more accurate forecasts when statistical forecasting methods are used

application of multi steps forecasting for restraining the bullwhip effect and improving inventory performance under autoregressive demand recent research suggests that the bullwhip effect or increasing variability of inventory replenishment orders as one moves up a supply chain illustrates inventory management inefficiencies this paper quantifies the bullwhip effect in the case of serially correlated external demand if autoregressive models are applied to obtain multiple steps demand forecasts a materials requirements planning mrp based inventory management approach is proposed to reduce the order variance simulation modeling is used to investigate the impact of the forecasting method selection on the bullwhip effect and inventory performance for the most downstream supply chain unit the mrp based approach is shown to reduce magnitude of the bullwhip effect while providing the inventory performance comparable to that of a traditional order up approach the application of autoregressive models compares favorably to other forecasting methods considered according to both the bullwhip effect and inventory performance criteria

revisiting the value of information sharing in two stage supply chains abstract there is a substantive amount of literature showing that demand information sharing can lead to considerable reduction of the bullwhip effect inventory costs the core argument analysis underlying these results is that the downstream supply chain member the retailer quickly adapts its inventory position to an updated end customer demand forecast however in many real life situations retailers adapt slowly rather than quickly to changes in customer demand as they cannot be sure that any change is structural in this paper we show that the adaption speed and underlying unknown demand process crucially affect the value of information sharing for the situation with a single upstream supply chain member manufacturer and a single retailer we consider two demand processes stationary or random walk these represent two extremes where a change in customer demand is never or always structural respectively the retailer and manufacturer both forecast demand using a moving average where the manufacturer bases its forecast on retailer demand without information sharing but on end customer demand with information sharing in line with existing results the value of information turns out to be positive under stationary demand one contribution though is showing that some of the existing papers have overestimated this value by making an unfair comparison our most striking and insightful finding is that the value of information is negative when demand follows a random walk and the retailer is slow to react slow adaptation is the norm in real life situations and deserves more attention in future research exploring when information sharing indeed pays off

supply chain forecasting when information is not shared the operations management literature is abundant in discussions on the benefits of information sharing in supply chains however there are many supply chains where information may not be shared due to constraints such as compatibility of information systems information quality trust and confidentiality furthermore a steady stream of papers has explored a phenomenon known as downstream demand inference ddi where the upstream member in a supply chain can infer the downstream demand without the need for a formal information sharing mechanism recent research has shown that under more realistic circumstances ddi is not possible with optimal forecasting methods or single exponential smoothing but is possible when supply chains use a simple moving average sma method in this paper we evaluate a simple ddi strategy based on sma for supply chains where information cannot be shared this strategy allows the upstream member in the supply chain to infer the consumer demand mathematically rather than it being shared we compare the ddi strategy with the no information sharing nis strategy and an optimal forecast information sharing fis strategy in the supply chain the comparison is made analytically and by experimentation on real sales data from a major european supermarket located in germany we show that using the ddi strategy improves on nis by reducing the mean square error mse of the forecasts and cutting inventory costs in the supply chain

non stationary demand forecasting by cross sectional aggregation in this paper the relative effectiveness of top down td versus bottom up bu approaches is compared for cross sectionally forecasting aggregate and sub aggregate demand we assume that the sub aggregate demand follows a non stationary integrated moving average ima process of order one and a single exponential smoothing ses procedure is used to extrapolate future requirements such demand processes are often encountered in practice and ses is one of the standard estimators used in industry in addition to being the optimal estimator for an ima process theoretical variances of forecast error are derived for the bu and td approach in order to contrast the relevant forecasting performances the theoretical analysis is supported by an extensive numerical investigation at both the aggregate and sub aggregate level in addition to empirically validating our findings on a real dataset from a european superstore the results demonstrate the increased benefit resulting from cross sectional forecasting in a non stationary environment than in a stationary one valuable insights are offered to demand planners and the paper closes with an agenda for further research in this area

smallholders institutional services and commercial transformation in ethiopia this article examines the role of institutional services of credit input supply and extension in the overall commercial transformation process of smallholder agriculture in ethiopia survey data collected in 2006 from 309 sample households in three districts of ethiopia are used for the analyses tobit regression models are used to measure the effect of access to services on the intensity of inputs use for fertilizer and agrochemicals a probit model is used to measure these effects on the adoption of improved seeds intensity of use of seeds is analyzed using an ordinary least squares model logarithmic cobb douglass functions are estimated to analyze the effect of access to services on crop productivity heckman s two stage estimation is used to examine determinants of household market participation and the extents of participation results show that access to institutional support services plays a significant role in enhancing smallholder productivity and market orientation our results imply that expanding and strengthening the institutional services is critical for the intensification and market orientation of smallholder agriculture in ethiopia in particular appropriate incentives and regulatory systems are urgently needed to encourage the involvement of the private sector in the provision of agricultural services

brazil s agrarian structure changes from 1970 through 1980 abstract structural patterns that accompany the growth and modernization of brazil s agrarian economy are identified despite increasing land concentration a rather large and disproportionate economic contribution of sizable numbers of very small farms is documented as is an enhanced vitality of larger farms meanwhile large quantities of unused agricultural land remain on many medium sized and large farms the expected inverse relationship between farm size and various measures of production per land unit is validated and reasons for the inverse relationship are deduced production is so large on small farms because their intensity of resource use overwhelms the facts that yields are greater and higher valued export crops are more usually found on large farms that capitalized intermediate and large farms seem destined to play a larger role in future production in brazil is argued but it is doubtful that the small farm and by implication the peasantry will disappear in the foreseeable future

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

forecasting with multivariate temporal aggregation the case of promotional modelling demand forecasting is central to decision making and operations in organisations as the volume of forecasts increases for example due to an increased product customisation that leads to more skus being traded or a reduction in the length of the forecasting cycle there is a pressing need for reliable automated forecasting conventionally companies rely on a statistical baseline forecast that captures only past demand patterns which is subsequently adjusted by human experts to incorporate additional information such as promotions although there is evidence that such process adds value to forecasting it is questionable how much it can scale up due to the human element instead in the literature it has been proposed to enhance the baseline forecasts with external well structured information such as the promotional plan of the company and let experts focus on the less structured information thus reducing their workload and allowing them to focus where they can add most value this change in forecasting support systems requires reliable multivariate forecasting models that can be automated accurate and robust this paper proposes an extension of the recently proposed muliple aggregation prediction algorithm mapa which uses temporal aggregation to improve upon the established exponential smoothing family of methods mapa is attractive as it has been found to increase both the accuracy and robustness of exponential smoothing the extended multivariate mapa is evaluated against established benchmarks in modelling a number of heavily promoted products and is found to perform well in terms of forecast bias and accuracy furthermore we demonstrate that modelling time series using multiple temporal aggregation levels makes the final forecast robust to model misspecification

farm size and productivity in malawian smallholder agriculture this article contributes to the limited literature on farm size and productivity in smallholder agriculture in sub saharan africa farm survey data and the results from a linear programming farm household model provide evidence for a positive relationship between farm size and productivity in both labour scarce and land scarce smallholder farming in malawi during the 1980 s the absence of an inverse relationship is explained in terms of failures in land capital and produce markets with acute capital constraints which affect both capital and labour inputs on smaller farms implications for rural development policies are discussed

land reform as commenced business the evidence against stopping abstract in the new paradigm institutions are long term endogenous thus the aims of land reform must be compatible with replace or substitute for initial incentives and power structures many reforms e g compulsory collectives are not redefinition of land reform is therefore needed yet the case for private land redistribution with ceilings remains the inverse relationship rests firmly on lower cost labor transactions in small farms though large but competitive transport or processing firms which enjoy lower cost capital transactions may be needed crucial is the impact of the postreform structure on livelihoods especially for the growing rural majority near landless workers new style market based reforms have potential probably best combined with old style ceilings substantial compensation with urban taxpayers sharing costs alternative off farm prospects and progressive taxes on large landholdings or bequests

an arima supply chain model this paper presents a multistage supply chain model that is based on autoregressive integrated moving average arima time series models given an arima model of consumer demand and the lead times at each stage it is shown that the orders and inventories at each stage are also arima and closed form expressions for these models are given the paper also discusses the causes of the bullwhip effect a phenomenon in which variation in demand produces larger variations in upstream orders and inventory this discussion reveals how different modeling can lead to different insights because they make different assumptions about the cause of the bullwhip effect these observations are used to develop managerial insights about reducing the bullwhip effect

determinants and effects of income diversification amongst farm households in burkina faso using four years of household data from three agroecological zones in burkina faso sahelian sudanian and guinean the article examines the determinants and effects of household income diversification harvest shortfalls and terms of trade are found to drive diversification but land constraints do not income diversification is associated with higher incomes and food consumption and more stable income and consumption over years

reduction of the value of information sharing as demand becomes strongly auto correlated information sharing has been identified in the academic literature as one of the most important levers to mitigate the bullwhip effect in supply chains a highly cited article on the bullwhip effect has claimed that the percentage inventory reduction resulting from information sharing in a two level supply chain when the downstream demand is autoregressive of order one is an increasing function of the autoregressive parameter of the demand in this paper we show that this is true only for a certain range of the autoregressive parameter and there is a maximum value beyond which the bullwhip ratio at the upstream stage is reduced and the percentage inventory reduction resulting from information sharing decreases towards zero we also show that this maximum value of the autoregressive parameter can be as high as 0 7 which represents a common value that may be encountered in many practical contexts this means that large benefits of information sharing cannot be assumed for those stock keeping units skus with highly positively auto correlated demand instead equally careful analysis is needed for these items as for those skus with less strongly auto correlated demand

investigating the added value of integrating human judgement into statistical demand forecasting systems abstract whilst the research literature points towards the benefits of a statistical approach business practice continues in many cases to rely on judgmental approaches for demand forecasting in today s dynamic environment it is especially relevant to consider a combination of both approaches however the question remains as to how this combination should occur this study compares two different ways of combining statistical and judgmental forecasting employing real life data from an international publishing company that produces weekly forecasts on regular and exceptional products two forecasting methodologies that are able to include human judgment are compared in a restrictive judgement model expert predictions are incorporated as restrictions on the forecasting model in an integrative judgment model this information is taken into account as a predictive variable in the demand forecasting process the proposed models are compared on error metrics and analysed with regard to the properties of the adjustments direction size and of the forecast itself volatility periodicity the integrative approach has a positive effect on accuracy in all scenarios however in those cases where the restrictive approach proved to be beneficial the integrative approach limited these beneficial effects the study links with demand planning by using the forecasts as input for an optimization model to determine the ideal number of skus per point of sale pos making a distinction between sku forecasts and sku per pos forecasts importantly this enables performance to be expressed as a measure of profitability which proves to be higher for the integrative approach than for the restrictive approach

returns to food and agricultural r d investments in sub saharan africa 1975 2014 research enabled growth in agricultural productivity is pivotal to sub saharan africa s overall economic growth prospects yet investments in research and development rd median 38 0 py around 78 5 of the evaluations relate to the commodity specific consequences of agricultural research while 5 5 report on the returns to an all agriculture aggregate the weight of commodity specific evaluation evidence is not especially congruent with the composition of agricultural production throughout africa nor to the best that can be determined the commodity orientation of public african agricultural r d

ramsey waits allocating public health service resources when there is rationing by waiting the optimal allocation of a public health care budget across treatments must take account of the way in which care is rationed within treatments since this will affect their marginal value we investigate the optimal allocation rules for public health care systems where user charges are fixed and care is rationed by waiting the optimal waiting time is higher for treatments with demands more elastic to waiting time higher costs lower charges smaller marginal welfare loss from waiting by treated patients and smaller marginal welfare losses from under consumption of care the results hold for a wide range of welfarist and non welfarist objective functions and for systems in which there is also a private health care sector they imply that allocation rules based purely on cost effectiveness ratios are suboptimal because they assume that there is no rationing within treatments

building african scientific capacity for agricultural development abstract during africa s first two decades of independence from 1960 to 1980 priority was given to increasing the size of national extension services because it was assumed that technology could be imported from industrial countries and the international agricultural research centers over the past decade donors have turned their attention to assisting national agricultural research systems nars but many nars are performing poorly and are faced with a high turnover of scientific staff and inadequate operating budgets moreover the present donor financed project by project and country by country approach to building african scientific capacity is seriously flawed this paper examines africa s agricultural research history over the past six decades and draws lessons for strengthening national and regional agricultural research systems over the coming 30 years

on bullwhip in a family of order up to policies with arma 2 2 demand and arbitrary lead times a number of papers have recently appeared that investigate the bullwhip effect the variance amplification of ordering decisions in the supply chain produced by the order up to replenishment policy an adapted policy with a proportional inventory position feedback controller has shown improved bullwhip behaviour the dynamic behaviour of this so called proportional order up to policy has been investigated for arbitrary lead times and several demand models such as i i d demand and autoregressive moving average ar 1 and arma 1 1 models it has been shown that for a correct choice of the feedback parameter the bullwhip effect can always be avoided however less attractive properties of this policy have also become clear herein we investigate the behaviour of the proportional order up to policy for arma 2 2 demand with arbitrary lead times in order to compensate for possible weaknesses of the proportional out policy we propose another replenishment rule that accounts for the characteristics of the demand in a superior manner the characteristics of both policies are compared for several parameter settings of the arma 2 2 model finally the consequences of our full state feedback order up to policy are discussed

contestable markets an uprising in the theory of industry structure presents a transcript of the presidential address delivered at the 94th meeting of the american economic association on december 29 1981 discussion of developments in the theory of industry structure welfare attributes of contestable markets behavior characteristics of oligopoly equilibrium intertemporal vulnerability to inefficient entry ebsco

the place of agricultural research in the development of sub saharan africa abstract outside sub saharan africa ssa agricultural research ar yields excellent returns why does ssa get so little from its major ar effort why do its ar scientists cost more yet produce less smallness of countries and research stations dispersion and high turnover make it hard to attain a critical mass of national ar scientists to remedy this they could concentrate on a few problems and crops yet they have neglected many of the most important e g cassava and overstressed export crops in other ways too european biases have distorted african ar socioeconomists moreover have entered research design too little and too late above all current domestic funds have been too scanty and unreliable to adequately support international and capital account ar efforts this lack of steady commitment illustrates ar s need for direction from clearer agricultural policy based on radically improved information and recognizing ssa s dramatic rise in labor land ratios guidelines for such policy are indicated within these a formalized and poverty oriented ar design system is suggested

sources of agricultural productivity growth and stagnation in sub saharan africa this paper examines sources of agricultural growth in sub saharan africa growth in the stock of traditional inputs land labor livestock remains the dominant source of output growth growth in modern input use was of secondary importance but still accounted for a 0 2 0 4 annual growth rate in three of four sub regions econometric results support earlier studies that suggest that land abundance may be a constraint on land productivity growth growth in agricultural exports and historic calorie availability had positive impacts on productivity these latter results suggest that positive feedback effects exist between export performance and food security on one hand and agricultural productivity on the other

optimal reimbursement health insurance and the theory of ramsey taxation this paper explores the trade off between risk sharing and the incentives to consume increased medical care inherent in reimbursement insurance the results for the theory of reimbursement insurance are compared with those on ramsey taxation it is shown that there is a close formal analogy and interpretations are given

creating rural livelihoods some lessons for south africa from experience elsewhere abstract a development path for south africa that will create jobs and reduce poverty must include the encouragement of greater labor intensity in agriculture especially of smallholder farming which was suppressed under apartheid there is however widespread skepticism on both the left and the right about the prospects for more labor intensive farming but this skepticism is called into question by both theory and evidence of the advantages of small scale production in certain products and circumstances there are now numerous examples of this in many parts of the world the paper discusses the preconditions for the development of such farming in south africa including land reform and the need to reorient investment and supporting economic and technical services research training marketing credit from the privileged large scale white farms to the undercapitalized and neglected black smallholders

user charges and priority setting in health care balancing equity and efficiency user charges are the major source of finance for many health care systems however traditional approaches to health care priority setting such as cost effectiveness analysis usually assume there are no user charges and therefore may ignore important implications for equity and efficiency this paper therefore develops a rudimentary model of priority setting in which the fixed health care budget can be augmented by user charges the paper uses methods analogous to models of optimal commodity taxation to develop a set of rules for the inclusion of a health technology in the subsidized health care package and the calculation of its associated copayment rate the results indicate that optimal levels of subsidy depend on the cost effectiveness of the intervention its price elasticity of demand the epidemiology of the associated disease and the policy maker s attitude towards equity the model has important implications for policy making in three domains health care priority setting evaluation of health care technologies and charging policy

demand forecasting with four parameter exponential smoothing abstract exponential smoothing methods are powerful tools for denoising time series predicting future demand and decreasing inventory costs in this paper we develop a smoothing and forecasting method that is intuitive easy to implement computationally stable and can satisfactorily handle both additive and multiplicative seasonality even when time series contain several zero entries and large noise component we start with the classical additive holt winters method and introduce an additional smoothing parameter in the level recurrence equation all parameters are required to lie within 0 1 and estimated by minimizing the one step ahead forecasting errors in the sample doing so the errors decrease substantially especially for the time series with strong trends the newly developed method produces more accurate short term out of sample forecasts than the classical holt winters methods and the holt winters methods with damped trend the performance of the method is evaluated using a battery of real quarterly and monthly time series from the m3 competition a simulation study is conducted for further in depth analysis of the method under different demand patterns we developed and justified the use of a symmetric relative efficiency measure that allows researchers ad practitioners to evaluate the performance of different smoothing and forecasting methods

a model for selecting the appropriate level of aggregation in forecasting processes abstract demand forecasting is a major issue in several industrial sectors a relevant choice for companies is the proper level of forecast aggregation forecasters need to properly identify what is the object of the forecasting process in terms of time bucket e g forecasts are produced on a daily level or on weekly one set of items the demand refers to e g single item or group of items set of locations the demand refers to e g single store or chain of stores managers can follow two basic approaches on the one hand they can adopt a detailed forecasting approach i e they can forecast demand for the item at the store by simply looking at the demand for the specific item store on the other hand they can adopt an aggregated forecasting approach in this paper we aim at figuring out what is the balance between the strengths and weaknesses of these two options and to identify the contingent variables that might lead managers to adopt one approach rather than the other in this paper we study the aggregation across locations by evaluating the components of forecasting error under the assumption of stationary demand finally we suggest metrics that one can adopt to support the choice of the appropriate forecasting process thus providing help to managers in defining the proper level of aggregation for a specific situation

the effects of integrating management judgement into out levels in or out of context physical inventories constitute a significant proportion of companies investments in today s competitive environment the trade off between customer service levels and inventory reserves is addressed in practice by statistical inventory software solutions given the tremendous number of stock keeping units skus that contemporary organizations deal with such solutions are fully automated however empirical evidence suggests that managers habitually judgementally adjust the output of such solutions such as replenishment orders or re order levels this research is concerned with the value being added or not when statistically derived inventory related decisions order up to out levels in particular are judgementally adjusted we aim at developing our current understanding on the effects of incorporating human judgement into inventory decisions to our knowledge such effects do not appear to have been studied empirically before and this is the first endeavour to do so a number of research questions are examined and a simulation experiment is performed using an extended database of approximately 1 800 skus from the electronics industry in order to evaluate human judgement effects the linkage between adjustments and their justification is also evaluated given the apparent lack of comprehensive empirical evidence in this area including the field of demand forecasting this is a contribution in its own right insights are offered to academics to facilitate further research in this area practitioners to enable more constructive intervention into statistical inventory solutions and software developers to consider the interface with human decision makers

the effects of integrating management judgement into intermittent demand forecasts empirical research suggests that quantitatively derived forecasts are very frequently judgementally adjusted nevertheless little work has been conducted to evaluate the performance of these judgemental adjustments in a practical demand sales context in addition the relevant analysis does not distinguish between slow and fast moving items currently there are neither conceptual developments nor empirical evidence on the issue of integrating judgements and statistical forecasts for slow intermittent demand items moreover no results have ever been reported on the stock control implications of these human judgements our work analyses monthly intermittent demand forecasts for the uk branch of a major international pharmaceutical company the company relies upon a commercially available statistical forecasting system to produce forecasts that are subsequently judgementally adjusted based on marketing intelligence gathered by the company forecasters the benefits of the intervention are evaluated by comparing the actual sales to system and final forecasts using both forecast accuracy and inventory control accuracy implication metrics our study allows insights to be gained on potential improvements to intermittent demand forecasting processes and subsequently the design effectiveness of forecasting support systems

household returns to land transfers in south africa a q squared analysis abstract the south african land reform programme has been widely criticised for its slow pace as well as its apparent lack of contribution to poverty reduction however there is little systematic evidence of the impact of land transfers on their beneficiaries due to data scarcity this paper combines econometric evidence based on official household surveys with qualitative data collected specifically to triangulate and complement the econometric analysis the qualitative data analysis confirms the plausibility of the econometric finding that on average beneficiaries do not gain from participation and suggests that the main reason for the disappointing impact of participation is the incompatibility of consultant led land use plans to land grantees skills

rural market imperfections and the farm size productivity relationship evidence from pakistan the subject of this article is the relationships between farm size and productivity and between farm size and profitability in the developing countries the recent controversies over the inverse size output relationship are reviewed and a framework is provided that explains the inverse relationship based on plausible assumptions about imperfections in the markets for labor land credit and risk from this framework a set of testable hypotheses are derived the hypotheses are tested on recent farm level panel data from pakistan a strong inverse relationship between farm size and yield is present in the sample even when household fixed effects are used to account for unobserved heterogeneity moreover the suggested market imperfections framework is consistent with the data

measuring and avoiding the bullwhip effect a control theoretic approach an important contributory factor to the bullwhip effect i e the variance amplification of order quantities observed in supply chains is the replenishment rule used by supply chain members first the bullwhip effect induced by the use of different forecasting methods in order up to replenishment policies is analysed variance amplification is quantified and we prove that the bullwhip effect is guaranteed in the order up to model irrespective of the forecasting method used thus when production is inflexible and significant costs are incurred by frequently switching production quantities up and down order up to policies may no longer be desirable or even achievable in the second part of the paper a general decision rule is introduced that avoids variance amplification and succeeds in generating smooth ordering patterns even when demand has to be forecasted the methodology is based on control systems engineering and allows important insights to be gained about the dynamic behaviour of replenishment rules

is small beautiful farm size productivity and poverty in asian agriculture the debate on the relationship between farm size and productivity has gone through a complete circle in the 1960s it was perceived that small farms were efficient because they can fully use their resources particularly family labor and they can monitor their production activities closely but in the 1970s and 1980s as many asian countries rapidly moved towards industrialization and urbanization small farms were considered a major obstacle in this process