aggregate dynamics of s s inventory management abstract this paper identifies the criteria for dynamic synchronization of the movement of agents who make intermittent adjustment to inventory stocks leading to harmonic resonance rather than cancellation i use a discrete markov process model of s s inventory adjustment to establish a theoretical framework for the aggregate dynamics and use simulations to demonstrate the distribution effects of a discrete model of lumpy behavior the paper identifies circumstances that lead to increased skewness of the distribution of agents over the inventory interval this has application in financial labor and commodity markets

bunching in the production process abstract this paper demonstrates that the variance of flows within the production process declines as the products move downstream from raw material deliveries toward completion thus the production process magnifies and transmits shocks within an industry to that industry s suppliers

frontiers of real time data analysis in the past ten years researchers have explored the impact of data revisions in many different contexts researchers have examined the properties of data revisions how structural modeling is affected by data revisions how data revisions affect forecasting the impact of data revisions on monetary policy analysis and the use of real time data in current analysis this paper summarizes many of the questions for which real time data analysis has provided answers in addition researchers and institutions have developed better real time data sets around the world still additional research is needed in key areas and research to date has uncovered even more fruitful areas worth exploring jel c52 c53 c80 e01

macroeconomic implications of production bunching factor demand linkages abstract existing empirical evidence suggests that output is more variable than consumption so that production smoothing is not apparently present in this paper we investigate some macroeconomic implications of the proposition that the empirical evidence reflects the presence of some firms in the economy that produce with nonconvex technologies overall when activities are sufficiently complementary and inventory holding is sufficiently costly nonconvexities at the firm level can generate a pattern of output and sales such that the variance of output exceeds that of sales at an aggregate level in this way nonconvexities at the individual firm level may have macroeconomic consequences

fixed costs of adjustment coordination and industry investment we test whether smooth industry level investment dynamics result from explicit aggregation of asynchronous and possibly lumpy firm level investment we compare the deviations of optimal from actual firm behavior across industries categorized by their ratios of idiosyncratic uncertainty to the sum of idiosyncratic and aggregate uncertainty the deviations are represented by the residuals of a cointegrating regression that is derived from the firm s first order condition under no adjustment costs in support of models with asynchronous firm decisions we find a significant negative relationship across industries between idiosyncratic uncertainty and the persistence of these residuals

transmission access and pricing with multiple separate energy forward markets california s congestion management protocols provide comparable access and prices to all users of the transmission system power exchange and bilateral contract parties the users implicitly bid for capacity on major transmission paths between zones the independent system operator iso allocates the available transmission capacity on these paths so that it maximizes the value of this capacity as measured by the users bids everyone scheduling flow on a congested path is charged the marginal cost based price for using the path the iso keeps each party s portfolio of generation and load individually in balance when adjusting schedules to relieve congestion on interzonal paths by keeping the portfolios of the different parties separate the iso clears its transmission market without arranging energy trades between parties parties are responsible for arranging their own trades the iso does not become involved in the energy forward markets

a multi sector inventory model abstract two competing paradigms for firm level inventory behavior are production smoothing and s s empirical evidence that aggregate production varies more than sales and inventory investment is positively correlated with sales appears to contradict the buffer stock production smoothing motivation work by blinder and maccini suggests that an s s model better explains these stylized facts i simulate a multi sector model with sequential interaction of heterogeneous agents representing manufacturing wholesale and retail agents who use either smoothing or s s inventory decision rules the results demonstrate that the stylized facts can be explained by a model of this type

macroeconomic implications of s s versus accelerator finished goods inventory strategies abstract large scale disaggregated simulation techniques involving 315 firms in 21 different industries holding 6 615 different stockpiles of purchased materials inputs are used to evaluate the implications for the stability of the economy of alternative strategies for managing inventories the simulations reveal that an s s form of production scheduling results in a somewhat less stable economy than is obtained with accelerator type inventory management

simulating the inventory cycle abstract simulations of the inventory cycle utilizing a model based on 84 interacting firms in 21 industries reveals that the ratio of the variance of sales to the variance of output is an unreliable indicator of how seriously firms attempt to smooth production or whether such efforts in the aggregate even out economic fluctuations it is also shown that the two slow estimates of the speed of adjustment reported in many econometric studies of united states data may result in part from aggregation bias rather than from limitations of the flexible accelerator model itself

taking stock a critical assessment of recent research on inventories empirical and theoretical aspects of inventory behavior became hot topics in the 1950s and early 1960s no one seemed to notice the tension that was developing between the emerging macroeconomic and microeconomic views of inventories macroeconomists routinely thought of inventories as a destabilizing factor yet the prevailing micro theory viewed inventories as a stabilizing factor it was a fascinating question that was barely explored instead somewhat inexplicably interest in inventories dried up as if inventories were of minor economic significance and little intrinsic interest by the early 1980s then economists once again knew something they had known in the 1950s that inventory investment is of first order importance in business cycles but they were also beginning to realize that the standard production smoothing buffer stock model of inventories was in deep trouble this paper focuses on developments since that realization

lumpy consumer durables market power and endogenous business cycles in this paper we show that lumpy consumer durables and market power can generate endogenous cycles consistent with the facts past sales determine the current market size of durable goods larger past sales ceteris paribus thus naturally result in a smaller current market size and income in this manner the seeds of a downturn are sown in an upturn jel classification e32 e13 biens de consommation durables en gros morceaux pouvoir de marche et cycles d affaires endogenes ce memoire montre que des biens de consommation durables en gros morceaux et du pouvoir de marche peuvent engendrer des cycles endogenes qui se calquent sur les chroniques observees les ventes passees determinent la taille du marche present pour les biens durables de plus grandes ventes dans le passe toutes choses etant egales par ailleurs resultent naturellement en un marche present plus petit et des revenus moindres de cette maniere le germe du declin est deja contenu dans l expansion

accounting for output fluctuations in manufacturing there is a substantial body of evidence to the effect that output is more volatile than sales among manufacturing industries numerous explanations have been advanced to account for this excess output volatility some examples are pro cyclical inventory movements induced by a stockout avoidance motive cost and technology shocks and decreasing marginal costs this article assesses the contribution of these different motives to output volatility for six different manufacturing industries linear quadratic models are estimated for each of the industries and then dynamic simulations are employed to determine the volatility of output when one or more of the factors are removed from the model technology shocks provide the most significant contribution to output volatility the stockout avoidance motive is also important cost shocks provide a very small contribution and marginal production costs are increasing at the margin and thus stabilize output it is also shown that output volatility declines when curre

evaluating predictions of change this article applies a technique developed by robert c merton 1981 and roy d henriksson and robert c merton 1981 for evaluating the market timing of financial managers to macroeconomic predictions of change this methodology may be used to determine whether the predictions may be of value to the user as an illustration the methodology is applied to a set of real gross national product forecasts copyright 1990 by the university of chicago

consumer durables and inertial behaviour estimation and aggregation of s s rules for automobile purchases the s s model originally introduced in the study of inventories see arrow et al 1951 scarf 1959 has recently received renewed attention both in the durable consumption and in the investment and labour demand literatures caballero 1993 for instance appeals to these type of models to explain the time series properties of durable expenditure and in particular the persistence or slow adjustment of such a variable in this paper i model the purchase behaviour of automobiles by u s households as an s s rule i estimate a flexible specification of such a rule using a large microeconomic data set and study some of the aggregate implications of this type of inertial behaviour the paper is one of the first attempts at estimating directly the parameters of an s s rule using micro data because of this some of the methodological issues concerning the specification and the estimation of s s rules are relevant for many potential applications furthermore the paper is one of the first to discuss and quantify the aggregate implications of an s s rule estimated on micro data in the presence of non convex transaction costs a full and consistent characterization of individual behaviour is very hard and typically requires strong restrictions grossman and laroque 1991 prove that an s s rule is optimal for a consumption and investment problem under very special circumstances some of their results were extended by eberly 1991 and beaulieu 1993a b eberly 1991 in particular has derived some closed form solutions for durable consumption in the presence of transaction costs while caballero and engel 1994 construct a model of investment where an s s rule is optimal the main problem with these theoretical results is that it is only possible to show optimality of s s rules under very stringent conditions in particular a necessary condition to derive them is that the optimization problem faced by an individual consumer can be reduced to a problem with a single state variable unfortunately as pointed out by bar ilan and blinder 1992 even simple generalizations are extremely difficult to analyse

the stabilizing effect of inventory in supply chains this paper presents a hierarchical model framework for the analysis of the stabilizing effect of inventories in multiechelon manufacturing distribution supply chains this framework is used to compare the variance of demand to the variance of replenishment orders at different echelons of the system e g retailer wholesaler empirical data and experience with management games suggest that in most industries inventory management policies can have a destabilizing effect by increasing the volatility of demand as it passes up through the chain the bullwhip effect our model helps to explain these observations and indicates mechanisms that can promote stabilization the analysis results also define sufficient conditions for the existence of stabilization and relate these conditions to the optimality of myopic control policies

s s inventory policies in general equilibrium we study the aggregate implications of s s inventory policies in a dynamic general equilibrium model with aggregate uncertainty firms in the model s retail sector face idiosyncratic demand risk and s s inventory policies are optimal because of fixed order costs the distribution of inventory holdings affects the aggregate outcome in two ways variation in the decision to order and variation in the rate of sale through the pricing decisions of retailers we find that both mechanisms must operate to reconcile observations that orders are more volatile than and inventory investment is positively correlated with sales while remaining consistent with other salient business cycle characteristics the model exhibits strong amplification for some shocks and persistence to a limited extent

information sharing in supply chains an empirical and theoretical valuation we provide an empirical and theoretical assessment of the value of information sharing in a two stage supply chain the value of downstream sales information to the upstream firm stems from improving upstream order fulfillment forecast accuracy such an improvement can lead to lower safety stock and better service based on the data collected from a consumer packaged goods company we empirically show that if the company includes the downstream sales data to forecast orders the improvement in the mean squared forecast error ranges from 7 1 to 81 1 across all studied products theoretical models in the literature however suggest that the value of information sharing should be zero for over half of our studied products to reconcile the gap between the literature and the empirical observations we develop a new theoretical model whereas the literature assumes that the decision maker strictly adheres to a given inventory policy our model allows him to deviate accounting for private information held by the decision maker yet unobservable to the econometrician this turns out to reconcile our empirical findings with the literature these decision deviations lead to information losses in the order process resulting in a strictly positive value of downstream information sharing furthermore we empirically quantify and show the significance of the value of operations knowledge the value of knowing the downstream replenishment policy this paper was accepted by serguei netessine operations management

aggregate inventory behavior in large european economies abstract inventory fluctuations are known to be an important propagation mechanism for u s business cycles this paper compares the significance of inventory fluctuations in the u s with four other major industrial economies in europe a general model of aggregate inventory demand is specified which seeks to encompass the models presented in recent studies of inventory behavior this model is estimated for the large european economies united kingdom west germany france and italy the preferred models that result from this analysis are compared with the empirical evidence for the u s

threshold behavior and aggregate fluctuation this paper concerns a propagation mechanism in an economy where many individuals follow a threshold rule and interact with a positive feedback we derive an asymptotic distribution of the propagation size when the number of the agents tends to infinity the propagation distribution exhibits a slower convergence to a deterministic value than it would if the agents followed a smooth adjustment policy this gives rise to significant aggregate fluctuations in a finite lumpy adjusting economy even when the agents are hit by small independent shocks

dynamic competition with random demand and costless search a theory of price posting this paper studies a dynamic model of perfectly competitive price posting under demand uncertainty firms must produce output in advance after observing aggregate sales in prior periods firms post prices for their unsold output in each period the demand of a new batch of consumers is randomly activated existing customers who have not yet bought and then new customers arrive at the market in random order observe the posted prices and either purchase at the lowest available price or delay their purchase decision we construct a sequential equilibrium in which the output produced and its allocation across consumers is efficient thus consumers endogenously sort themselves efficiently with the highest valuations purchasing first transaction prices in each period rise continuously as firms become more optimistic about demand followed by a market correction by the last period prices are market clearing

stochastic cascades credit contagion and large portfolio losses abstract we analyze an interactive model of credit ratings where external shocks spread by a contagious chain reaction to the entire economy counterparty relationships along with discrete adjustments of credit ratings generate a transition mechanism that allows the financial distress of one firm to spill over to its business partners the spread of financial distress constitutes a source of intrinsic risk for large portfolios of credit sensitive securities that cannot be diversified away we provide a characterization of the fluctuations of credit ratings in large economies when adjustments follow a threshold rule and analyze the effects of downgrading cascades on credit portfolios

measuring the efficacy of inventory with a dynamic input output model abstract this paper extends the recently developed dynamic inoperability input output model diim for assessing productivity degradations due to disasters inventory policies are formulated and incorporated within the diim to evaluate the impact of inventories on the resilience of disrupted interdependent systems the inventory diim can provide practical insights to preparedness decision making through explicit tradeoff analysis of multiple objectives including inventory costs and economic loss reductions the model is demonstrated in several illustrative examples to depict various nuances of inventory policies the paper then culminates in a case study that utilizes input output and inventory accounts from the bureau of economic analysis

a measure of bullwhip effect in supply chains with a mixed autoregressive moving average demand process abstract in this paper we quantify the impact of the bullwhip effect the phenomenon in which information on demand is distorted as moving up a supply chain for a simple two stage supply chain with one supplier and one retailer assuming that the retailer employs a base stock inventory policy and that the demand forecast is performed via a mixed autoregressive moving average model arma 1 1 we investigate the effects of the autoregressive coefficient the moving average parameter and the lead time on the bullwhip effect

market timing recent development and a new test abstract henriksson merton s market timing test suffers nontrivial size distortion when the event forecast is autocorrelated a new test is suggested to detect the dependence of two autocorrelated binary time series it complements the existing tests due to better test power

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

directional forecasts of gdp and inflation a joint evaluation with an application to federal reserve predictions many studies have undertaken separate analyses of the fed s forecasts of real gross domestic product gdp growth and inflation this article presents a method for jointly evaluating the direction of change predictions of these variables we conclude that some of the inflation forecasts examined separately were not valuable however the joint pattern of gdp and inflation projections was generally in accord with the economy s movements directional forecasting is now an increasingly popular metric for forecasting performance pesaran and timmermann 2004 414

the variability of aggregate demand with s s inventory policies this paper develops a general theory of the aggregate implications of s s inventory policies it is shown that s s policies add to the variability of demand with the variance of orders exceeding the variance of sales overall the s s theory contradicts the widely held notion that retail inventories act as a buffer protecting manufacturers from fluctuating sales in 1951 arrow harris and marschak 3 introduced the s s form of inventory policy the policies are designed for retailers of finished goods who face economies of scale when placing orders with their suppliers to pursue an s s inventory policy the retailer establishes a lower stock point s and an upper stock point s no order is placed until inventories fall to s or below whereupon they are restored to the maximum of s a general proof of the optimality of these s s inventory policies was provided by scarf 13 at the microeconomic level the model has been extensively investigated formulae are available to compute optimal policies e g ehrhardt 6 and these policies are xidely used in industry e g schwartz ed 14 in addition the model has been extended to increasingly complex demand environments e g karlin and fabens 11 in contrast little is known about the macroeconomic implications of s s policies several recent papers have begun to correct this deficiency akerlof has suggested that pursuit of constant threshold money holding policies of the s s variety might be responsible for the observed low short run income elasticity of the demand for money akerlof 1 and akerlof and milbourne 2 in the operations research literature ehrhardt schultz and wagner 7 analyzed the demand environment of a wholesaler supplying several retailers they required that the distinct retailers have independent sales ruling out the analysis of common factors in sales finally simulation results of blinder 4 suggested a role for the s s model in understanding retail sector inventories however the theoretical difficulties with the model remained unresolved blinder commented if firms have a technology that makes the s s rule optimal aggregation across firms is inherently difficult indeed it is precisely this difficulty which has prevented the s s model from being used in empirical work to date blinder 4 p 459 in this paper we present a general theory of the aggregate implications of s s policies our central finding is that s s policies add to the variability of demand with the variance of orders exceeding the variance of sales this result holds even in the presence of common factors in retail sales in addition a close connection

the bullwhip effect progress trends and directions the bullwhip effect refers to the phenomenon where order variability increases as the orders move upstream in the supply chain this paper provides a review of the bullwhip literature which adopts empirical experimental and analytical methodologies early econometric evidence of bullwhip is highlighted findings from empirical and experimental research are compared with analytical and simulation results assumptions and approximations for modelling the bullwhip effect in terms of demand forecast delay replenishment policy and coordination strategy are considered we identify recent research trends and future research directions concerned with supply chain structure product type price competition and sustainability

the resurgence of inventory research what have we learned abstract recent empirical and theoretical research on business inventories is surveyed and critically evaluated while most inventory research has had macroeconomic motivations we focus on its microtheoretic basis and on potential conflicts between theory and evidence the paper asks two principal questions first how can inventories which are allegedly used by firms to stabilize production nonetheless be a destabilizing factor at the macroeconomic level second why if firms are following the production smoothing model is production more variable than sales in many industries we suggest that the so called s s model may help answer both questions

inventories markups and real rigidities in menu cost models a growing consensus in new keynesian macroeconomics is that nominal cost rigidities rather than countercyclical markups account for the bulk of the real effects of monetary policy shocks we revisit these conclusions using theory and data on inventories we study an economy with nominal rigidities in which goods are storable our theory predicts that if costs of production are sticky and markups do not vary much in response to say expansionary monetary policy firms react by excessively accumulating inventories in anticipation of future cost increases in contrast if the data inventories are fairly constant over the cycle and in response to changes in monetary policy we show that costs must increase and markups must decline sufficiently in times of a monetary expansion in order to reduce firm s incentive to hold inventories and thus bring the model s inventory predictions in line with the data versions of the model consistent with the dynamics of inventories in the data imply that countercyclical markups account for a sizable fraction of the response of real variables to monetary shocks

economic theory and the world of practice a celebration of the s s model it was the question of how best to balance the costs of ordering and of running out of stock against the costs of holding excess inventory that inspired kenneth arrow theodore harris and jacob marschak to introduce the s s model in 1951 in this celebratory article we show how this model not only answered important practical questions but also opened the door to a quite startling range of important and challenging follow up questions many of great practical importance and analytic depth the s s model has become one of the touchstone models of economics opening new vistas of applied economic theory to all who internalize its structure today it is universally applied to solve questions faced in inventory control the core model elements uncertainty and fixed costs of adjustment are ubiquitous which has resulted in its becoming the general purpose economic model of discrete adjustment the s s model has also become a profound source of inspiration for macroeconomists seeking to understand the role that discrete microeconomic adjustments play in macroeconomic fluctuations looking forward we foresee rapid growth in the use of s s modeling to aid households making complex and costly financial decisions such as when and how to terminate a mortgage in the projected era of household operations research new modeling challenges will arise due to enriched feedback from the world of practice

inventories and the business cycle an equilibrium analysis of s s policies we develop an equilibrium business cycle model where nonconvex delivery costs lead firms to follow s s inventory policies calibrated to postwar us data the model reproduces two thirds of the cyclical variability of inventory investment moreover it delivers strongly procyclical inventory investment greater volatility in production than sales and a countercyclical inventory to sales ratio our model challenges several prominent claims involving inventories including the widely held belief that they amplify aggregate fluctuations despite the comovement between inventory investment and final sales gdp volatility is essentially unaltered by inventory accumulation because procyclical inventory investment diverts resources from final production thereby dampening fluctuations in sales

transmission management for congested power system a review of concepts technical challenges and development of a new methodology transmission networks have some constraints that should be addressed in order to ensure sufficient control to maintain the security level of a power system while maximising market efficiency the most obvious drawback of transmission constraints is a congestion problem that becomes an obstacle to perfect competition among the market participants since it can influence spot market pricing as the power flow violates transmission constraints redispatching generating units is required and this will cause the price at every node to vary this manuscript presents concepts technical challenges and methodology for investigating an alternative solution to the redispatch mechanism and then formulates lmp scheme using an optimisation technique that may well control congestion as the main issue the lmp scheme are varied and improved to take into account the energy price congestion revenue cost of losses as well as the transmission usage tariff by utilising shift factor based optimal power flow sf opf which is derived from the well known dc optimal power flow dc opf model

inventory performance under pack size constraints and spatially correlated demand abstract motivated by a problem facing a large retailer we consider the impact of pack size on the performance of a periodic review inventory system in the presence of spatial i e between retailers correlation of demand which we model using an equicorrelated multivariate poisson distribution employing simulation we utilise a full factorial experiment to provide support for decisions on product and supplier selection and whether or not packs should be split during distribution we consider variables such as pack size correlation and the number of branches and discuss how they and their interactions impact performance metrics such as inventory and shortage levels and the bullwhip effect

pitfalls in market timing test abstract henriksson and merton s market timing test suffers nontrivial size distortion when the observations are serially dependent sequences potential danger of finding spurious timing ability can be avoided by implementing a markov regression that includes the lagged dependent variables as additional explanatory variables

a panel data study on spanish firms inventory investment this paper raises several questions about inventory investment of a sample of 172 big nonfinancial spanish companies inventory investment has been usually explained by two alternative theories the production smoothing model and the s s model first we provide a descriptive analysis based on industry level data to show some shortcomings of the first model then we test a flexible accelerator model using firm level data the results seem to show that inventory investment previous period inventories and sales are closely and significantly related this evidence although not conclusive rejects both the pure production smoothing model and the s s model at the same time our results confirm the view of a target inventory level and the plausibility of the so called stock adjustment model so that the optimal inventory holding buffers sales volatility

foreign exchange rate expectations micro survey data this paper analyzes the panel data of biweekly surveys on the yen dollar exchange rate expectations of forty four institutions for two years and contains four major findings first market participants are heterogeneous that is significant individual effects exist in their expectation formation second the individual effects have a characteristic of wishful expectations exporters expect yen depreciation and importers expect yen appreciation relative to others third many violate the rational expectations hypothesis fourth forecasts with long horizons show less yen appreciation than those with short horizons cross equation constraints implied by the consistency of the forecast term structure are strongly rejected in the data copyright 1990 by american economic association

financing constraints and inventories abstract this paper investigates the impact of financing constraints on firms inventory and cash management in particular it examines the extent to which the presence of such constraints may account for certain empirical regularities these include e g the excess variance of production vis a vis that of sales as well as the counter cyclicality and persistence of the inventory sales ratio we model the intertemporal decision making on production cash retention and dividends of a firm that is exposed to stochastic demand shocks in every period and faces constrained access to external sources of finance it is found that the presence of financing constraints can explain the excess variance of production in a model which otherwise would not deliver this result moreover as long as demand is positively serially correlated they also contribute to the counter cyclicality and persistence of the inventory sales ratio the paper suggests that financing constraints should not be discarded as a factor driving the cyclical behaviour of inventories

aggregation and optimization with state dependent pricing the literature on the aggregation of s s policies has ignored the impact of aggregate behavior on the individual s optimization problem in the case of pricing the feedback effects are clear not only do pricing strategies determine the evolution of the price level but the evolution of the price level also influences the optimal pricing strategies in this paper we provide a consistent treatment of aggregation and optimization we use this model to analyze three issues in the menu cost pricing literature the relationship between strategic complementarity and the real effects of money the relationship between the variance of the money supply and the correlation between money and output and the relationship between the cost of price adjustment and the size of price adjustment questions concerning the dynamics of aggregate variables such as prices employment investment and consumption represent the core of business cycle analysis one striking feature of these variables is the radical difference between properties of these aggregates and the nature of the individual behavior that underlies them the behavior of a firm s prices investment and employment and the behavior of an individual s consumption all involve frictional elements that lead to discrete adjustment at the microeconomic level heterogeneity among individuals however tends to smooth the behavior of the corresponding aggregates in recent years a large body of research has developed to examine the manner in which microeconomic frictions influence aggregate dynamics one of the centerpieces of this research has been the s s model developed by arrow harris and marschak 1951 the key element of this model is the state dependence of individual decisions agents act when a state variable crosses some critical threshold which balances the cost and benefits of adjustment the aggregate implications of this form of microeconomic behavior have been analyzed by blinder 1981 caplin 1985 and mosser 1991 in the context of inventory dynamics by caplin and spulber 1987 caballero and engel 1991 1993 and caplin and leahy 1991 in the context of prices and by bertola and caballero 1990 caballero 1993 and eberly 1994 in the context of con sumer durables one of the most limiting aspects of these models is that they focus exclusively on the impact that microeconomic inertia has on aggregate dynamics they 1we would like to thank michael harrison loannis karatzas john leahy sr andreu mas colell a co editor and four anonymous referees for helpful discussions and comments and the national science foundation and the sloan foundation for financial support

a microsimulated model of inventories in interfirm competition abstract producers management of inventories of finished goods are studied with a computer simulation that depicts the interactions of a group of firms with their customers customers give orders that have a random component to their current customary suppliers and will attempt to switch to another firm if stockouts cause bad service the firms are shown experimenting to find rules of inventory management that avoid loss of customers yet incur low costs average inventories and costs under the rules that firms arrive at rise non linearly with the variance of customer orders the simulated firms respond to higher interest rates by substantial cuts in average inventories held the costs firms incur when changing the level of production also affects the rule that firms select unless firms are able to take advantage of each others experience wide variation in behavior among firms is likely under such a scenario

business as usual market crashes and wisdom after the fact the authors present a three stage model of market dynamics in the first stage routine behavior tends to keep information of common interest trapped in private hands in the second stage private information reaches a threshold that triggers some agents to alter their behavior these actions release information to the market the final stage involves the market s response to this news as other participants react to the initial departure from routine behavior the authors present an application to industry investment they also outline applications to the international debt crisis to bank runs and to political upheavals copyright 1994 by american economic association

what inventories tell us about aggregate fluctuations a tractable approach to s s policies abstract we estimate a dsge model with s s inventory policies we find that i taking inventories into account can significantly improve the empirical fit of dsge models in matching the standard business cycle moments in addition to explaining inventory fluctuations ii s s inventory policies can significantly amplify aggregate output fluctuations in contrast to the findings of the recent general equilibrium inventory literature and iii aggregate demand shocks become more important than technology shocks in explaining the business cycle once inventories are incorporated into the model an independent contribution of our paper is that we develop a solution method for analytically solving s s inventory policies in general equilibrium models with heterogeneous firms and a large aggregate state space and we illustrate how standard log linearization methods can be used to solve various versions of our inventory model generate impulse response functions and estimate the model s deep structural parameters

bullwhip effect measurement and its implications the bullwhip effect or demand information distortion has been a subject of both theoretical and empirical studies in the operations management literature in this paper we develop a simple set of formulas that describe the traditional bullwhip measure as a combined outcome of several important drivers such as finite capacity batch ordering and seasonality our modeling framework is descriptive in nature as it features certain plausible approximations that are commonly employed in practical inventory systems the results are nonetheless compelling and can be used to explain various conflicting observations in previous empirical studies building on the theoretical framework we discuss the managerial implications of the bullwhip measurement we show that the measurement can be completely noninformative about the underlying supply chain cost performance if it is not linked to the operational details such as decision intervals and leadtimes specifically we show that an aggregated measurement over relatively long time periods can mask the operational level bullwhip in addition we show that masking also exists under product or location aggregation in some illustrative cases

inventories and risk in african manufacturing using a panel data set for zimbabwe which includes firm specific measures of contractual risk we show that contractual risk has a major effect on the holding input stocks and to a lesser extent the constitution of cash reserves this is consistent with inventories being a hedge against stockout risk by contrast firms facing more inter annual market risk hold less inventories this suggests that african manufacturers prefer adapting to long term market fluctuations as they materialise rather than building up inventories this interpretation is consistent with the finding that high market risk firms also have a low capacity utilisation rate

an evaluation of survey exchange rate forecasts abstract a non parametric test of direction is employed to evaluate the survey forecasts provided by the money market services empirical results suggest that the forecasts are useful for predicting the direction of exchange rate changes the results are consistent with a weaker form of rationality than unbiasedness

decentralized approach to intermarket congestion management when transmission bottlenecks affect dispatches and prices of neighboring regional transmission organization rto markets intermarket congestion management and coordination are needed to mitigate congestion and to compute economically efficient prices in the day ahead markets this paper discusses and proposes two decentralized processes with which each rto administers its energy market and also acts as a transmission coordinator to achieve feasible and efficient use of congested transmission by all markets in the region interconnection with this arrangement a new decomposition technique is introduced without breaking a network model at the rto s geographical boundaries the paper then presents two decentralized congestion management formulations to model markets interactions in the interconnection the coordination between market operators and transmission operators is based on the use of congestion price signals or allocated megawatt capacities as well as their sensitivity information the proposed solution ensures not only feasible schedules but also efficient and consistent congestion path prices for the final schedules in the entire interconnection numerical examples are given to illustrate the application of the proposed models

a directional evaluation of corporate executives exchange rate forecasts we investigate the directional accuracy of exchange rate forecasts by corporate executives we find that a forecast with a 1 year horizon is valuable for the profitability and unprofitability predictions of manufacturers although previous studies provide considerable evidence that forecasts with horizons of 1 year and longer are not valuable however a forecast is not valuable in predicting an appreciation or depreciation of the exchange rate our findings suggest that corporate executives are more concerned about and focused on the impact of the exchange rate on their profitability rather than the exchange rate itself

an empirical investigation of dynamic ordering policies adaptive base stock policy is a well known tool for managing inventories in nonstationary demand environments this paper presents empirical tests of this policy using aggregate firm level data first we extend a single item adaptive base stock policy in previous literature to a multi item case second we transform the policy derived for the multi item case to a regression model that relates firm level inventory purchases to firm level sales and changes in sales forecasts we focus on two research questions can the adaptive base stock policy explain cross sectional ordering behaviors under sales growth to the extent that the adaptive base stock policy fails to explain ordering behaviors under sales growth are there frictions that explain such a finding our empirical results demonstrate disparities in ordering behaviors between firms experiencing high and moderate sales growth contrary to theoretical prediction this implies that inventory purchases are a function of not only current sales and changes in sales forecast but also past sales growth as potential explanations for this departure from theoretical prediction we show that both future demand dynamics and inventory holding risks depend on past sales growth in addition we find that firms inventory holding risks may also be affected by purchasing constraints imposed by supply chain contracts our results provide managerial implications for practitioners and inform future theoretical research this paper was accepted by martin lariviere operations management

can the production smoothing model of inventory behavior be saved the production smoothing model of inventory behavior has a long and venerable history and theoretical foundations that seem very strong yet certain overwhelming facts seem not only to defy explanation within the production smoothing framework but actually to argue that the basic idea of production smoothing is all wrong most prominent among these is the fact that the variance of detrended production exceeds the variance of detrended sales this paper first documents the stylized facts then it derives the production smoothing model rigorously and explains how the model can be amended to make it consistent with the facts finally it reviews the theoretical and empirical evidence and tries to draw some tentative conclusions

are government and imf forecasts useful an application of a new market timing test abstract we investigate the directional accuracy of gdp and price forecasts by the japanese government and the imf with a new method developed by pesaran and timmermann pesaran m h timmermann a 2009 testing dependence among serially correlated multi category variables journal of the american statistical association 485 325 337 extending the literature to government forecasts our results illustrate an empirical application of the new test our findings provide positive evidence about the usefulness of imf forecasts whereas they cast doubts about government forecasts

optimal price dynamics and speculation with a storable good this paper analyzes as a dynamic game the optimal price and storage strategies of respectively a the seller of a storable good who must keep pace with inflation but incurs a cost to changing his price b his customers who speculate on the timing of price adjustments to buy and store just before a unique markov perfect equilibrium is shown to exist and is fully characterized rt generally involves a phase of mixed strategies during which the seller tries to deter speculation by injecting uncertainty into its price dynamics while speculators store in increasing numbers with possibly a final run on the good the stochastic price policies of a large number of such firms are shown to aggregate back to a price index growing at the rate of general inflation in response to which they arose the model thus establishes that a a constant rate of aggregate inflation can at the same time generate and cover up significant uncertainty and social costs at the microeconomic level b speculation can be destabilizing and socially wasteful even in the absence of shocks and imperfect information most importantly they provide a theoretical foundation for the frequently encountered claim that inflation causes price uncertainty