technological regimes schumpeterian patterns of innovation and firm level productivity growth the paper investigates the relationships between technological regimes and firm level productivity performance and it explores how such a relationship differs in different schumpeterian patterns of innovation the analysis makes use of a rich dataset containing data on innovation and other economic characteristics of a large representative sample of norwegian firms in manufacturing and service industries for the period 1998 2004 first we decompose tfp growth into technical progress and efficiency changes by means of data envelopment analysis we then estimate an empirical model that relates these two productivity components to the characteristics of technological regimes and a set of other firm specific factors the results indicate that 1 tfp growth has mainly been achieved through technical progress while technical efficiency has on average decreased 2 the characteristics of technological regimes are important determinants of firm level productivity growth but their impacts on technical progress are different from the effects on efficiency change 3 the estimated model works differently in the two schumpeterian regimes technical progress has been more dynamic in schumpeter mark ii industries while efficiency change has been more important in schumpeter mark i markets

environmental regulation industrial innovation and green development of chinese manufacturing based on an extended cdm model abstract as for the academics and policymakers more attention has been given to the issue on how to drive green development of the manufacturing through regulations and innovations we construct the extended crepon duguet mairesse cdm model and employ the panel data of chinese manufacturing industries during 2003 2014 to examine the effects of environmental regulation on industrial innovation and green development the findings reveal that 1 in the long term environmental regulation has crowded out r d investment 2 environmental regulation has inhibited patent outputs so that the weak version of porter hypothesis is not underpinned 3 in the short term environmental regulation has promoted the improvements of labor productivity energy efficiency and environmental efficiency in the manufacturing industry excluding green total factor productivity gtfp whereas in the long term environmental regulation only has increased energy efficiency while it has obstructed labor productivity which provides no support for the strong version of porter hypothesis 4 different innovation outputs have distinct influences on labor productivity energy efficiency environmental efficiency and gtfp finally this paper provides pertinent policy implications

on the structure of lost sales inventory models we provide a new approach to the structural analysis of the standard lost sales inventory system this approach is we think easier to work with than the original one we also derive new bounds on the optimal policy then we show that more variable demand leads to higher cost finally we extend the analysis to several important variations of the basic model

optimal strategic oil stockpiling and import tariffs the case of china abstract as two of the most important instruments for dealing with the issues of energy supply security strategic petroleum reserves sprs and oil import tariffs have been proven effective in developed countries while china is currently building up its strategic oil reserves to ensure energy security it is of great importance to investigate china s optimal oil stockpiling policies while taking into account the possibility of imposing an import tariff or quota which can also be used for alleviating the energy insecurity of an oil importing country employing a dynamic programming framework this paper examines the optimal spr policies and oil import tariffs or quotas for china and the interactions between the two instruments under different scenarios for the world oil market the results show that the combination of optimal tariffs and spr policies can substantially reduce the expected oil insecurity cost for china the effect is larger when the probability that a disruption will continue is higher

demand seasonality in retail inventory management abstract we investigate the value of accounting for demand seasonality in inventory control our problem is motivated by discussions with retailers who admitted to not taking perceived seasonality patterns into account in their replenishment systems we consider a single location single item periodic review lost sales inventory problem with seasonal demand in a retail environment customer demand has seasonality with a known season length the lead time is shorter than the review period and orders are placed as multiples of a fixed batch size the cost structure comprises of a fixed cost per order a cost per batch and a unit variable cost to model retail handling costs we consider four different settings which differ in the degree of demand seasonality that is incorporated in the model with or without within review period variations and with or without across review periods variations in each case we calculate the policy which minimizes the long run average cost and compute the optimality gaps of the policies which ignore part or all demand seasonality we find that not accounting for demand seasonality can lead to substantial optimality gaps yet incorporating only some form of demand seasonality does not always lead to cost savings we apply the problem to a real life setting using point of sales data from a european retailer we show that a simple distinction between weekday and weekend sales can lead to major cost reductions without greatly increasing the complexity of the retailer s automatic store ordering system our analysis provides valuable insights on the tradeoff between the complexity of the automatic store ordering system and the benefits of incorporating demand seasonality

analysis of tailored base surge policies in dual sourcing inventory systems we study a model of a firm managing its inventory of a single product by sourcing supplies from two supply sources a regular supplier who offers a lower unit cost and a longer lead time than a second emergency supplier a practically implementable policy for such a firm is a tailored base surge tbs policy allon g van mieghem ja 2010 global dual sourcing tailored base surge allocation to near and offshore production management sci 56 1 110 124 to manage its inventory under this policy the firm procures a constant quantity from the regular supplier in every period and dynamically makes procurement decisions for the emergency supplier allon and van mieghem describe this practice as using the regular supplier to meet a base level of demand and the emergency supplier to manage demand surges and they conjecture that this practice is most effective when the lead time difference between the two suppliers is large we confirm these statements in two ways first we show the following analytical

understanding corporate coherence theory and evidence abstract multiproduct firms are perceived to be coherent in their scope yet there is no strong theoretical foundations to explain coherence in modern industrial organization theory this paper shows that as u s manufacturing firms grow more diverse they maintain a constant level of coherence between neighboring activities this finding runs counter to the idea that firms with many activities are generally more incoherent a framework is then presented which appeals to the nature of enterprise learning path dependencies and the nature of the selection environment to explain the ubiquity of coherent diversifiers

pricing option contracts on the strategic petroleum reserve in this article we examine the pricing of option contracts on the strategic petroleum reserve spr and consider how these can be used by both the government and refiners we analyze the interaction between the call and put option contracts taking into account the underlying game in the infinite markov decision process with discounting explaining the relationship between the valuation of options on the spr by refiners and the valuation of financial options on a marker crude in financial markets we conclude that the values of both call and put options on the spr increase with oil prices and decrease with total inventory furthermore our analysis shows that a more active management of the spr creates higher social welfare although refiners profit less from inventories and larger volatility in inventory profits decreasing private investment in petroleum stocks

the outlook for us oil dependence abstract oil dependence is defined as a dynamic problem of short and long run market power the potential monopoly power of an oil cartel depends on its market share and the elasticities of oil supply and demand while the economic vulnerability of oil consuming states depends most directly on the quantity of oil imported and the oil cost share of gross domestic product gdp of these factors only the market share of the organization of petroleum exporting countries opec cartel and the rate of growth of world oil demand are clearly different than they were 25 years ago opec still holds the majority of world oil and in the future will regain market share a hypothetical 2 year supply reduction in 2005 2006 similar in size to those of 1973 1974 or 1979 1980 illustrates the potential benefits to opec and harm to the us economy of a future oil price shock opec s revenues are estimated to increase by roughly 0 7 trillion while the us economy loses about 0 5 trillion strategic petroleum reserves seem ineffective against a determined multi year supply curtailment increasing the market s price responsiveness by improving the technologies of oil supply and oil demand can greatly reduce the costs of oil dependence each element of this interpretation of the oil dependence problem is well supported by previous studies this paper s contribution is to unite these elements into a coherent explanation and to point out the enormously important implications for energy policy

inventory models with shelf age and delay dependent inventory costs in this paper we show how any model with a general shelf age dependent holding cost and delay dependent backlogging cost structure may be transformed into an equivalent model in which all expected inventory costs are level dependent we develop our equivalency results first for periodic review models with full backlogging of stockouts these equivalency results permit us to characterize the optimal procurement strategy in various settings and to adopt known algorithms to compute such strategies for models in which all or part of stockouts are lost we show that the addition of any shelf age and delay dependent cost structure does not complicate the structure of the model beyond what is required under the simplest i e linear holding and backlogging costs we proceed to show that our results carry over to continuous review models with demands generated by compound renewal processes the continuous review models with shelf age and delay dependent carrying and backlogging costs are shown to be equiva

sources procedures and microeconomic effects of innovation fabio arcangeli paul david frank engelman christopher freeman massimo moggi richard nelson luigi orsenigo nathan rosenberg michele salvati g n von tunzelman two anonymous referees and the participants at the meeting of the committee on distribution growth and technical progress of the italian national research council cnr rome november 16 1985 have helped with various redraftings a particularly grateful acknowledgment is for the insightful and patient help of moses abramovitz this work has been undertaken at the science policy research unit spru university of sussex as part of the research program of the designated research centre sponsored by the economic and social research council esrc earlier support to the research that led to this paper by the italian national research council cnr is also gratefully acknowledged the statistical research has been undertaken with the assistance of stephano brioschi ilaria fornari and giovannu prennushi

a model based on stochastic dynamic programming for determining china s optimal strategic petroleum reserve policy china s strategic petroleum reserve spr is currently being prepared but how large the optimal stockpile size for china should be what the best acquisition strategies are how to release the reserve if a disruption occurs and other related issues still need to be studied in detail in this paper we develop a stochastic dynamic programming model based on a total potential cost function of establishing sprs to evaluate the optimal spr policy for china using this model empirical results are presented for the optimal size of china s spr and the best acquisition and drawdown strategies for a few specific cases the results show that with comprehensive consideration the optimal spr size for china is around 320 million barrels this size is equivalent to about 90 days of net oil import amount in 2006 and should be reached in the year 2017 three years earlier than the national goal which implies that the need for china to fill the spr is probably more pressing the best stockpile release action in a disruption is related to the disruption levels and expected continuation probabilities the information provided by the results will be useful for decision makers

a comparison of the optimal costs of two canonical inventory systems we compare two inventory systems one in which excess demand is lost and the other in which excess demand is backordered both systems are reviewed periodically they experience the same sequence of identically and independently distributed random demands holding and shortage costs are considered the holding cost parameter is identical however the cost of a lost sale could be different from the per period cost of backlogging a unit sale when these costs are equal we prove that the optimal expected cost for managing the system with lost sales is lower when the cost of a lost sale is greater we establish a relationship between these parameters that ensures that the reverse inequality is true these results are useful for designing inventory systems we also introduce a new stochastic comparison technique in this paper

the u s patent system in transition policy innovation and the innovation process abstract this paper surveys the major changes in patent policy and practice that have occured in the last two decades in the u s and reviews the existing analyses by the economists that attempt to measure the impacts these changes have had on the processes of technological change it also reviews the broader theoretical and empirical literature that bears on the expected effects of changes in patent policy despite the significance of the policy changes and the wide availability of detailed data relating to patenting robust conclusions regarding the empirical consequences for technological innovation of changes in patent policy are few possible reasons for these limited results are discussed and possible avenues for future research are suggested

revenue management for operations with urgent orders this article is motivated by the case of a company manufacturing industrial equipment that faces two types of demand on the one hand there are the so called regular orders for installations or refurbishing of existing facilities these orders have a relatively long lead time on the other hand there are urgent orders mostly related to spare parts when a facility has a breakdown the delay in such case is much shorter but higher margins can be obtained we study the order acceptance problem for a firm that serves two classes of demand over an infinite horizon the firm has to decide whether to accept a regular order or equivalently how much capacity to set aside for urgent orders in order to maximize its profit we formulate this problem as a multi dimensional markovian decision process mdp we propose a family of approximate formulations to reduce the dimension of the state space via aggregation we show how our approach can be used to compute bounds on the profit associated with the optimal order acceptance policy finally we show that the value of revenue management is commensurate with the operational flexibility of the firm

closing the gap a learning algorithm for lost sales inventory systems with lead times we consider a periodic review single product inventory system with lost sales and positive lead times under censored demand in contrast to the classical inventory literature we assume the firm d

optimal strategic petroleum reserve policies a steady state analysis a simple model is presented which allows us to determine the optimal size fillup and drawdown rates for a strategic petroleum reserve spr under a variety of supply and demand conditions the optimal policy variables are determined by minimizing an analytic expression which we derive for the expected insecurity cost rate to the u s due to uncertainty in supply of imported oil the oil market is modeled in terms of an elastic demand curve and two levels of supply which alternate according to a stationary continuous time markov process the spr policy is characterized by a fixed fillup rate up to the reserve s capacity when supply is at its normal level and a fixed drawdown rate during shortages the insecurity cost rate being minimized includes consumer welfare loss due to price hikes reserve holding cost and capital appreciation of the reserve base case results and sensitivity analysis are presented and compared to results obtained by previous approaches these comparisons suggest that the proposed model can reasonably approximate the more computationally demanding stochastic dynamic programming formulation the main advantage of the new approach is that it permits extensive sensitivity analysis which is important given the quality of the data

stockpile strategy for china s emergency oil reserve a dynamic programming approach abstract china is currently accelerating construction of its strategic petroleum reserves how should china fill the spr in a cost effective manner in the short run how might this affect world oil prices using a dynamic programming model to answer these questions the objective of this paper is to minimize the stockpiling costs including consumer surplus as well as crude acquisition and holding costs the crude oil acquisition price in the model is determined by global equilibrium between supply and demand demand in turn depends on world market conditions including china s stockpile filling rate our empirical study under different market conditions shows that china s optimal stockpile acquisition rate varies from 9 to 19 million barrels per month and the optimal stockpiling drives up the world oil price by 3 7 the endogenous price increase accounts for 52 of total stockpiling costs in the base case when the market is tighter or the demand function is more inelastic the stockpiling affects the market more significantly and pushes prices even higher alternatively in a disruption drawdown from the stockpile can effectively dampen soaring prices though the shortage is likely to leave the price higher than before the disruption

opportunities incentives and the collective patterns of technological change in a few pages in the introductory article for this debate vernon ruttan succeeds in the unlikely task of flagging many issues at the core of the economic interpretation of technological change and by doing so he implicitly addresses also a few sensitive spots for the economic discipline at large here i will not attempt to provide any thorough view of what i consider the achievements and limitations of the current state of the art see however freeman i 994 for a critical survey which i largely share rather i shall put forward a series of remarks which hopefully could be seen as part of a much wider and still largely unexplored research programme as a premise just note that some form of attention to technology related phenomena has spread over the last 20 30 years from small enclaves of heterodox economists and economic historians to become an important concern even for quite mainstream theories of e g the firm industrial organisation macroeconomics trade growth etc from patent races all the way to new trade and new growth theories and even real business cycle macro models technical change has drawn a consideration which is less by default than it was say in robert solow s original growth models orjoe bain s barriers to entry views on industrial structures and in parallel empirical studies at the levels of specific technologies firms sectors and countries have boomed for overviews cf dosi i988 nelson i993 freeman i982 i 994 cohen i 995 and granstrand i 994 among others so at least in this sense those decreasing returns to the economics of technical change suggested by ruttan do not seem to have set in however ruttan s paper raises also substantive questions about the relative success of three interpretative perspectives which he calls induced evolutionary and path dependent in the following i shall argue that an evolutionary perspective broadly defined can easily accommodate both inducement effects and path dependent patterns of technical change let me start from what i consider the major building blocks of an

asymptotic optimality of order up to policies in lost sales inventory systems we study a single product single location inventory system under periodic review where excess demand is lost and the replenishment lead time is positive the performance measure of interest is the long run average holding cost and lost sales penalty cost for a large class of demand distributions we show that when the lost sales penalty becomes large compared to the holding cost the relative difference between the cost of the optimal policy and the best order up to policy converges to zero for any given cost parameters we establish a bound on this relative difference numerical experiments show that the best order up to policy performs well yielding an average cost that is within 1 5 of the optimal cost when the ratio between the lost sales penalty and the holding cost is 100 we also propose a heuristic order up to level using two newsvendor expressions in our experiments the cost of this order up to policy is 2 52 higher on an average than the best order up to policy

an empirical analysis of the dynamic programming model of stockpile acquisition strategies for china s strategic petroleum reserve abstract the world s future oil price is affected by many factors the challenge therefore is how to select optimal stockpile acquisition strategies to minimize the cost of maintaining a reserve this paper provides a new method for analyzing this problem using an uncertain dynamic programming model to analyze stockpile acquisition strategies for strategic petroleum reserve using this model we quantify the impact of uncertain world oil price on optimal stockpile acquisition strategies of china s strategic petroleum reserve for the period 2007 2010 and 2011 2020 our results show that the future stockpile acquisition is related to oil prices and their probability and if not considering the occurrence of oil supply shortage china should at least purchase 25 million barrels when world oil price is at an optimal level the optimal price of stockpile acquisition of every year has a stronger relationship with the probability of high price and the optimal expected price and size of stockpile acquisition is different in each year

sectoral patterns of technical change towards a taxonomy and a theory abstract the purpose of the paper is to describe and explain sectoral patterns of technical change as revealed by data on about 2000 significant innovations in britain since 1945 most technological knowledge turns out not to be information that is generally applicable and easily reproducible but specific to firms and applications cumulative in development and varied amongst sectors in source and direction innovating firms principally in electronics and chemicals are relatively big and they develop innovations over a wide range of specific product groups within their principal sector but relatively few outside firms principally in mechanical and instrument engineering are relatively small and specialised and they exist in symbiosis with large firms in scale intensive sectors like metal manufacture and vehicles who make a significant contribution to their own process technology in textile firms on the other hand most process innovations come from suppliers these characteristics and variations can be classified in a three part taxonomy based on firms 1 supplier dominated 2 production intensive 3 science based they can be explained by sources of technology requirements of users and possibilities for appropriation this explanation has implications for our understanding of the sources and directions of technical change firms diversification behaviour the dynamic relationship between technology and industrial structure and the formation of technological skills and advantages at the level of the firm the region and the country

inventory cost rate functions with nonlinear shortage costs this article considers five cost rate models for inventory control each summarizing the expected holding and shortage costs per period as a function of the inventory position all models have linear holding costs and shortage cost coefficients of dimension unit period unit and period the latter two coeficients may be the shadow costs of a fill rate and a ready rate service constraint respectively one of the cost rate models is a new suggestion intended to facilitate modeling of periodic review inventory systems if and only if conditions on the demand process are presented for which the cost rate is quasi convex in the inventory position the typical sufficient condition requires that the cumulative demand distribution be logconcave a condition that is met by most demand distributions commonly used in the inventory literature the results simplify optimization and extend the known optimality of s s and nq r policies to cost structures common in applications and to the presence of typical service constraints as a prerequisite for the study a series of new monotonicity results are derived for compound renewal processes

oil stockpiles and import reductions a dynamic programming approach this paper analyzes oil stockpiling policies using models in which u s policy choices are restricted to just two instruments stockpiles and disruption tariffs the model considers the influence of u s and in general oecd import demands upon the opec price for oil and the duration and severity of oil disruptions induced by disturbances among the opec nations our development is based upon a probabilistic view of disruptions analyzed by applying dynamic programming

intellectual property protection in plant varieties a worldwide index 1961 2011 in this paper we construct a new index measuring the strength of intellectual property ip protection for plant varieties in 69 countries over the period 1961 2011 we examine the statistical properties of the index and compare it with other indicators of ip protection we conclude that the index provides a reasonable synthetic assessment of the relative strength of ip protection in plant varieties across countries in addition we study the main determinants of the evolution of the index and examine the patterns of correlation between the index and agricultural production

strategic oil stockpiling for energy security the case of china and india abstract compared with the developed countries the developing countries could be more vulnerable to oil supply disruptions due to their lack of strategic petroleum reserves sprs several developing countries including china and india are establishing their sprs to ensure energy security in the common world oil market one country s spr decisions can be affected by the decisions of other countries this paper investigates the spr policies of china and india two of the largest developing countries in a game theoretic framework where the interactions between the two countries are taken into account the results show that players equilibrium stockpiling strategies and total expected costs could vary significantly with the initial oil market state stockpile acquisition capacity and the probabilities for disruptions to persist

inventory control in directed networks a note on linear costs we consider periodic review inventory control problems in directed networks primary examples of which are distribution systems and assembly systems external demand could occur at each node when inventory is insufficient to meet requirements at a node a portion of this demand is backordered and the remaining is lost external demands as well as lead times for inventory purchase assembly and transportation are stochastic in each period linear sales revenues and the following costs all linear are charged at each node a inventory purchase assembly transfer cost to receive inventory b holding cost c backorder cost and d lost sales cost when the objective function of interest is a discounted sum of profits over a finite planning horizon it is shown that the sales prices and the inventory purchase assembly transfer cost parameters can be assumed to be zero without loss of generality the result is proved for every realization of demands and lead times some extensions to these results are discussed during this process we also generalize the concept of echelon inventories to directed networks

a dynamic programming model of china s strategic petroleum reserve general strategy and the effect of emergencies abstract to protect the security of energy supply china is building national strategic petroleum reserve spr we present a dynamic programming model to determine the optimal stockpiling and drawdown strategies for china s spr under various scenarios focusing on minimizing the total cost of reserves in contrast to previous research the oil price given in our model is exogenous on a monthly instead of annual basis with a view to more realistic simulation of optimal strategies each year our model results show that in the case where stockpiling affects oil prices a given spr size will be achieved earlier than when stockpiling does not affect oil prices in different emergency conditions the optimal stockpiling and drawdown strategies of china s spr are very different when an emergency occurs the shock of stockpiling on the oil price per barrel could range 0 49 6 35 while the impact of drawdown on the oil price per barrel could range 6 22 to 0 48

a stochastic dynamic nash game analysis of policies for managing the strategic petroleum reserves of consuming nations in this paper we present a nash dynamic game model of interactions among oil inventory and tariff policies for oil importing countries the inventory policies consist of the rates for building up and drawing down strategic oil reserves while the tariff policies consist of setting tariffs as a function of the state of the world oil market the model represents a stochastic game in which countries are grouped into two players where each player in the game chooses its individual policies to maximize expected social welfare we use the model to present empirical results about the sizes of the stockpiles as a function of disruption probabilities tariff policies and cooperation versus noncooperation between nations in addition to results regarding the build up and draw down rates as a function of the amount of disruption or probability of future disruption our central conclusion is that build up and drawdown policies are essentially the same with or without international cooperation due to the current inventory limits on u s and foreign strategic petroleum reserves

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

china s optimal stockpiling policies in the context of new oil price trend abstract optimizing the size of oil stockpiling plays a fundamental role in the process of making national strategic petroleum reserve spr policies there have been extensive studies on the operating strategies of spr however previous literatures have paid more attention to a booming or stable international oil market while few studies analyzed the impact of a long term low oil price on spr policy as a supplement this paper extends a static model to study china s optimal stockpiling policy under different oil price trends and in response to different current oil prices a new variable fc which demonstrates the appreciation and depreciation of the reserved oil economic value has been taken into account to assess the optimal size of spr in this paper a more multi perspective of view is provided to consider the policies of china s spr especially under the different trend of international oil price fluctuations

when should we use strategic oil stocks the countries of the oecd have built significant strategic oil stocks over the past 30 years and others like india and china have begun substantial programs as well the operating environment for using those stocks in an emergency however has changed considerably during those years the original plan for a multilateral draw down of strategic reserves has been amended and repeatedly modified as events have warranted but there remains a great deal of uncertainty as to how and when strategic stocks should be used this paper discusses the track record of using strategic reserves and concludes with recommendations for new guidelines for their use which will strengthen their utility to both the policymaker and the marketplace

foreign competition domestic knowledge base and innovation activities evidence from chinese high tech industries using panel data analysis for a sample of chinese high technology industries from 1998 to 2008 this study examines how industry characteristics affect industry innovation activities differing from existing studies our research considers the impact of foreign competition on innovation activities at industry level in a large emerging economy the results indicate that the intensity of competition from foreign invested enterprises fies and domestic skill intensity affect industry buy and make activities foreign competition is positively associated with the intensity of buy activity but negatively affects the intensity of make activity further the findings show that domestic skill intensity weakens the impact of foreign competitive pressure on innovation activities our empirical evidence has important policy implications

how much should society fuel the greed of innovators on the relations between appropriability opportunities and rates of innovation the paper attempts a critical assessment of both the theory and the empirical evidence on the role of appropriability and in particular of intellectual property rights iprs as incentives for technological innovation we start with a critical discussion of the standard justification of the attribution of ipr in terms of market failures in knowledge generation such an approach we argue misses important features of technological knowledge and also neglects the importance of non market institutions in the innovation process next we examine the recent changes in the ipr regimes and their influence upon both rates of patenting and underlying rates of innovation the evidence broadly suggests that first iprs are not the most important device apt to profit from innovation and second they have at best no impact or possibly even a negative impact on the underlying rates of innovation rather we argue technology and industry specific patterns of innovation are primarily driven by the opportunities associated with each technological paradigm conversely firm specific abilities to seize them and profit from innovation depend partly on adequacy of the strategic combinations identified by the taxonomy of teece d 1986 profiting from technological innovation implications for integration collaboration licensing and public policy research policy 15 285 305 and partly on idiosyncratic capabilities embodied in the various firms

technical note inventory systems with a generalized cost model we study a single stage inventory system with a generalized shortage penalty cost that includes the following three components i a cost that is an increasing function of the number of backordered units in a period ii a fixed cost incurred for each period in which there is a backorder irrespective of how many units are backordered and finally iii a cost that is an increasing function of the number of periods a customer is backordered we show the problem can be transformed into one in which the backorder cost depends on the inventory position only then we present two sets of conditions the first one restricts our attention to a special case of the generalized penalty cost model while the second one restricts our attention to stationary demand models with some distributional assumptions under the first resp second set of conditions we show that the expected cost in a period can be expressed as a convex resp quasiconvex function of the after ordering inventory position we use this property to prove the optimality of order up to policies under both sets of conditions and discuss extensions to the cases where either a fixed ordering cost or a batch ordering constraint is present

leaders and followers perspectives on the nordic model and the economics of innovation abstract what kinds of social and economic systems are most conducive to innovation we formulate a simple model in which countries can close the gap with the technological leader but where the cost of doing so may be so high that the country chooses to remain laggards observed disparities in productivity may be the result of a recognition that the cost of closing the gap exceeds benefit and there may therefore exist an international equilibrium in which there are leaders and followers even if it is granted that the united states is the leader and scandinavia are followers there are theoretical grounds for arguing that the nordic model may in fact be better for innovation suggesting that if the us adopted some of the nordic institutions innovations would be higher and societal welfare would be improved even more

on the sources and significance of interindustry differences in technological opportunities abstract the set of technological opportunities in a given industry is one of the fundamental determinants of technical advance in that line of business we examine the concept of technological opportunity and discuss three categories of sources of those opportunities advances in scientific understanding and technique technological advances originating in other industries and in other private and governmental institutions and feedbacks from an industry s own technological advances data from the yale survey on industrial research and development are used to measure the strength of various sources of technological opportunity and to discern interindustry differences in the importance of these sources we find that interindustry differences in the strength and sources of technological opportunities contribute importantly to explanations of cross industry variation in r d intensity and technological advance

robustness of order up to policies in lost sales inventory systems we study an inventory system under periodic review when excess demand is lost it is known huh et al 2009 that the best base stock policy is asymptotically optimal as the lost sales penalty cost parameter grows we now show that this result is robust in the following sense consider the base stock level which is optimal in a backordering system with a per unit per period backordering cost in which the backorder cost parameter is a function of the lost sales parameter in the original system then there is a large family of functions mapping the lost sales cost parameter to the backorder cost parameter such that the resulting base stock policy is asymptotically optimal we also demonstrate the robustness phenomenon through a second result we consider the base stock level which is optimal in a backordering system in which a unit of backorder is charged a penalty cost only once such a system has been studied by rosling we show that this base stock policy is also asymptotically optimal furthermore we show that a modification suggested by archibald of this base stock level also results in an asymptotically optimal policy finally we numerically test the performance of this heuristic policy for a wide spectrum of values for the lost sales penalty cost parameter and illustrate the superior performance of archibald s method

profits r d and innovation a model and a test in this article we investigate both conceptually and empirically the relationships between three interconnected elements of the schumpeterian engine of progress the ability of industries rd the ability of innovations to lead to high entrepreneurial profits the commitment of industries to invest profits in further technological efforts we build a simultaneous three equation model with appropriate lags and we test it at industry level for 38 manufacturing and service sectors on eight european countries over two time periods from 1994 to 2006 the results show that the model effectively accounts for the dynamics of european industries

a dynamic nash game model of oil market disruptions and strategic stockpiling in this paper we present and analyze a nash dynamic game model for investigating public and private sector oil inventory policies in unstable world oil markets conceptual results about the model include simple verifiable conditions for uniqueness and stability of solutions along with characterizations of optimal policies we also present results and discuss computational issues that arise in determining subgame perfect infinite horizon equilibria using a steady state policy iteration approach

a dynamic inventory model with the right of refusal we consider a dynamic inventory production model with general convex order production costs and excess demand that can be accepted or refused by the firm excess demand that is accepted is backlogged and results in a backlog cost whereas demand that is refused results in a lost sales charge endogenizing the sales decision is appropriate in the presence of general convex order costs so that the firm is not forced to backlog a unit whose subsequent satisfaction would reduce total profits in each period the firm must determine the optimal order and sales strategy we show that the optimal policy is characterized by an optimal buy up to level that increases with the initial inventory level and an order quantity that decreases with the initial inventory level more importantly we show the optimal sales strategy is characterized by a critical threshold a backlog limit that dictates when to stop selling this threshold is independent of the initial inventory level and the amount purchased we investigate various properties of this new policy as demand stochastically increases the amount purchased increases but the amount backlogged decreases reflecting a shift in the way excess demand is managed we develop two regularity conditions one that ensures some backlogs are allowed in each period and another that ensures the amount backlogged is nondecreasing in the length of the planning horizon we illustrate the buy up to levels in our model are bounded above by buy up to levels from the pure lost sales and pure backlogging models we explore additional extensions using numerical experiments

a threshold inventory rationing policy for service differentiated demand classes motivated by a study of the logistics systems used to manage consumable service parts for the u s military we consider a static threshold based rationing policy that is useful when pooling inventory across two demand classes characterized by different arrival rates and shortage stockout and delay costs the scheme operates as a q r policy with the following feature demands from both classes are filled on a first come first serve basis as long as on hand inventory lies above a threshold levelk once on hand inventory falls below this level low priority i e low shortage cost demand is backordered while high priority demand continues to be filled we analyze this static policy first under the assumption that backorders are filled according to a special threshold clearing mechanism structural results for the key performance measures are established to enable an efficient solution algorithm for computing stock control and rationing parameters i e q r andk numerical results confirm that the solution under this special threshold clearing mechanism closely approximates that of the priority clearing policy we next highlight conditions where our policy offers significant savings over traditional round up and separate stock policies encountered in the military and elsewhere finally we develop a lower bound on the cost of the optimal rationing policy numerical results show that the performance gap between our static threshold policy and the optimal policy is small in environments typical of the military and high technology industries

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

the effect of intellectual property rights on agricultural productivity this article explores how the strengthening of intellectual property ip protection affects agricultural productivity in a panel of countries for the period 1961 2011 using an index of ip protection for plant varieties we study the effect of stronger intellectual property rights iprs on cereal yields and two different types of cereals open pollinated wheat and hybrid maize we found that the strengthening of iprs has a positive effect on productivity of cereals for high and low income countries however we found no significant effect for middle income countries in addition we found that becoming a member of the trade related aspects of intellectual property rights negatively affects cereal yields finally we found evidence of the existence of nonlinearities in the effect of iprs on agricultural yields which confirms a threshold effect of iprs that also varies for countries of different income level the findings support the hypothesis that country specificities are important in determining the effect of iprs and imply that there is no unique system that fits all

inventory rationing in a make to stock production system with several demand classes and lost sales this paper considers the stock rationing problem of a single item make to stock production system with several demand classes and lost sales for the case of poisson demands and exponential production times we show that the optimal policy can be characterized by a sequence of monotone stock rationing levels for each demand class there exists a stock rationing level at or below which it is optimal to start rejecting the demand of this class in anticipation of future arrival of higher priority demands a simple queueing model is analyzed to compute the operating cost of a rationing policy in a numerical study we compare the optimal rationing policy with a first come first served policy to investigate the benefit of stock rationing under different operating conditions of the system

imitation costs and patents an empirical study it has long been recognised that the costs of imitating new products have an important effect on the incentives for innovation in a market economy as arrow i962 and others have pointed out if firms can imitate an innovation at a cost that is substantially below the cost to the innovator of developing the innovation there may be little or no incentive for the innovator to carry out the innovation in their discussions of the innovation process economists frequently have called attention to the major role played by the costs of imitation but there has been little or no attempt to measure these costs to test various hypotheses concerning the factors influencing them or to estimate their effects in this paper we report some findings of what seems to be the first study of this topic in addition we present data regarding the effects of patents on imitation costs and on the rate of innovation

average cost single stage inventory models an analysis using a vanishing discount approach an important problem in the theory of dynamic programming is that of characterizing sufficient conditions under which the optimal policies for markov decision processes mdps under the infinite horizon discounted cost criterion converge to an optimal policy under the average cost criterion as the discount factor approaches 1 in this paper we provide for stochastic inventory models a set of such sufficient conditions these conditions unlike many others in the dynamic programming literature hold when the action space is noncompact and the underlying transition law is weakly continuous moreover we verify that these conditions hold for almost all conceivable single stage inventory models with few assumptions on cost and demand parameters as a consequence of our analysis we partially characterize for the first time optimal policies for the following inventory systems under the infinite horizon average cost criterion which have thus far been a challenge a capacitated systems with setup costs b uncapacitated systems with convex ordering costs plus a setup cost and c systems with lost sales and lead times

a single product inventory model for multiple demand classes we consider a single product inventory system that serves multiple demand classes which differ in their shortage costs or service level requirements we assume a critical level control policy and a backorder clearing mechanism in which we treat a backorder for a lower priority class equivalent to a reserve stock shortfall for the higher priority class we show the equivalence between this inventory system and a serial inventory system based on this equivalence we develop a model for cost evaluation and optimization under the assumptions of poisson demand deterministic replenishment lead time and a continuous review q r policy with rationing we propose a computationally efficient heuristic and develop a bound on its performance we provide a numerical experiment to show the effectiveness of the heuristic and the value from a rationing policy finally we describe how to extend the model to permit service times and how to extend the model to a multi echelon setting

on limiting or encouraging rivalry in technical progress the effect of patent scope decisions abstract this essay is on the effects of the scope of a patent e g how broad its allowed claims on subsequent inventing in a field it is argued that this depends on the topography of technical advance in a field in particular on how inventions are linked to each other and in the extent to which rapid technical advance requires a diversity of actors and minds as contrasted with being facilitated by express coordination of inventive activity technical advance is examined in several different fields with a focus on how patents influenced the pace and quality of development the authors conclude that allowing and enforcing broad patent claims tends to hinder technical progress

the impact of opec on east asian oil import security a multidimensional analysis abstract east asian countries such as china japan and south korea are major importers in the international oil market therefore oil import security is critical to sustainable economic development in these countries this paper uses a modified two stage dea like model to investigate the impact of the organization of petroleum exporting countries opec on oil import security in the east asian region over time specifically three dimensional variables were introduced to the model the opec internal dimension the opec and asian country interaction dimension and the international external dimension the empirical results show a substantial difference between china and the other two countries in terms of these dimensions although the impact of opec on china s oil security has increased over time its impact on japan has declined political uncertainty in opec countries and oil price volatility are the major issues for china whereas cost is the key area of concern for japan south korea s concerns are less clear the results of this study lay an important foundation for discussing policy issues involved in regional cooperation integration and sustainable growth in the east asian region

to protect or not to protect modes of appropriability in the small enterprise sector abstract what appropriation strategies are chosen by innovative small firms a cluster analysis of data from the german cis was carried out to indentify four distinct modes of appropriability in the small enterprise sector the results show that for many innovative small firms the key question is not whether to use intellectual property rights iprs or not but whether to protect their innovations from imitation at all furthermore formal and informal innovation protection mechanisms should not be seen as mutually exclusive since several are employed jointly secrecy and lead time advantages over competitors are often combined with iprs yet a number of small firms use complexity of design as a substitute to patent protection the relevance of each appropriation mode depends on such factors as the degree of innovativeness the type of innovator and the general market environment which implies that the importance of iprs is limited to specific business contexts furthermore regarding firm performance as measured by innovation effects some evidence is found that choosing both ipr and non ipr oriented appropriation strategies can prove to be effective in achieving company goals taken all together the study implies that the use of iprs by innovative small firms is highly selective the paper concludes with a discussion of the implications for policy and research

the patent paradox revisited an empirical study of patenting in the u s semiconductor industry 1979 1995 we examine the patenting behavior of firms in an industry characterized by rapid technological change and cumulative innovation recent survey evidence suggests that semiconductor firms do not rely heavily on patents to appropriate returns to r d yet the propensity of semiconductor firms to patent has risen dramatically since the mid1980s we explore this apparent paradox by conducting interviews with industry representatives and analyzing the patenting behavior of 95 u s semiconductor firms during 1979 1995 the results suggest that the 1980s strengthening of u s patent rights spawned patent portfolio races among capital intensive firms but it also facilitated entry by specialized design firms

150 years of patent protection this paper examines three sets of explanations for variations in the strength of patent protection across sixty countries and a 150 year period wealthier nations are more likely to have patent systems to allow patentees a longer time to put their patents into practice and to ratify treaties assuring equal treatment of other nations but they are also likely to charge higher fees and limit patent protection in some important ways countries with democratic political institutions are consistently more likely to have patent protection appear to be determined by historical factors the origin of a country s commercial law appears particularly important in explaining the presence of restrictions on patentees privileges and discriminatory provisions against foreign patentees this abstract was borrowed from another version of this item

the value of intellectual property rights to firms and society economists view intellectual property rights iprs as policy tools for encouraging innovation but they recognize that they can also inhibit competition there are many types of iprs and institutions concerned with their administration we begin by outlining how these complex and varied rights are supposed to work and how they interact with other characteristics of firms and markets we then survey the available literature on patents trade marks and copyright to assess the value of these iprs to firms and the costs to firms of acquiring and defending their rights the paper concludes with suggestions for topics requiring further research to inform public policy better

energy security coping with multiple supply risks this study starts from the observation that today s western trading nations are exposed to multiple risks of energy supplies eg simultaneous shortage of oil and gas supplies to cope with these risks both oil and gas can be stockpiled adopting the viewpoint of a policy maker who aims at minimizing the expected cost of security of supply optimal simultaneous adjustments of oil and gas stocks to exogenous changes such as an increase in the probability of supply disruption are derived against this benchmark one dimensional rules such as oil reserves for 90 days turn out to be not only suboptimal but also to suggest adjustments exacerbating suboptimality

periodic review lost sales inventory models with compound poisson demand and constant lead times of any length in almost all literature on inventory models with lost sales and periodic reviews the lead time is assumed to be either an integer multiple of or less than the review period in a lot of practical settings such restrictions are not satisfied we develop new models allowing constant lead times of any length when demand is compound poisson besides an optimal policy we consider pure and restricted base stock policies under new lead time and cost circumstances based on our numerical results we conclude that the latter policy which imposes a restriction on the maximum order size performs almost as well as the optimal policy we also propose an approximation procedure to determine the base stock levels for both policies with closed form expressions

intellectual property rights hinder sequential innovation experimental evidence abstract in this paper we contribute to the discussion on whether intellectual property rights foster or hinder innovation by means of a laboratory experiment we introduce a novel scrabble like word creation task that captures most essentialities of a sequential innovation process we use this task to investigate the effects of intellectual property allowing subjects to impose license fees on their innovations we find intellectual property to have an adverse effect on welfare as innovations become less frequent and less sophisticated introducing communication among innovators does not reduce this detrimental effect introducing intellectual property results in more basic innovations with subjects failing to exploit the most valuable sequential innovation paths subjects act more self reliant and non optimally in order to avoid paying license fees our results suggest that granting intellectual property rights hinders innovation especially for sectors characterized by a strong sequentiality in innovation processes

using stockpile delegation to improve china s strategic oil policy a multi dimension stochastic dynamic programming approach abstract there has been much attention paid to oil security in china in recent years although china has begun to establish its own strategic petroleum reserve spr to prevent potential losses caused by oil supply interruptions the system aiming to ensure china s oil security is still incomplete this paper describes and provides evidence for the benefits of an auxiliary strategic oil policy choice which aims to strengthen china s oil supply security and offer a solution for strategic oil operations with different holding costs in this paper we develop a multi dimension stochastic dynamic programming model to analyze the oil stockpile delegation policy which is an intermediate policy between public and private oil stockpiles and is appropriate for the chinese immature private oil stockpile sector the model examines the effects of the oil stockpile delegation policy in the context of several distinct situations including normal world oil market conditions slight oil supply interruption and serious oil supply interruption operating strategies that respond to different oil supply situations for both the spr and the delegated oil stockpile were obtained different time horizons interruption times and holding costs of delegated oil stockpiles were examined the construction process of china s spr was also taken into account

continuous review s s policies with lost sales a method is developed to calculate an s s policy that minimizes the average stationary cost in an inventory system with constant lead time fixed order cost linear holding cost per unit time linear penalty cost per unit short discrete compound poisson demand and lost sales it is assumed that at most one order is outstanding or equivalently that s s s the procedure is compared to several easier to compute approximate solutions including one that assumes backordering examples are given that reveal that although the backorder solution is different than the lost sales one the cost penalty of using it in the lost sales situation is small

inventory control with information about supply conditions this paper presents an inventory control model which includes a markovian model of the supply system as that system evolves over time so do the replenishment leadtimes the optimal policy has the same structure as in standard models but its parameters change dynamically to reflect current supply conditions in this setting contrary to conventional wisdom a longer leadtime does not necessarily imply more inventory the leadtime is important but so is a concept we call order coverage

coordinating inventory control and pricing strategies under batch ordering in this paper we investigate joint pricing and inventory control problems in a finite horizon single product periodic review setting with certain uncertain supply capacities the demands in different periods are random variables whose distributions depend on the posted price exhibiting the additive form the order quantity in each period is required to be of integral multiples of a given specific batch size denoted by q inventory replenishment incurs a linear ordering cost referred to as the cost rate function the sum of holding and backorder costs can either be convex or quasi convex the objective is to determine a joint ordering and pricing decision that can maximize the total expected profit over the planning horizon we first consider the case in which the cost rate function is convex and show that the modifiedr q list price policy is optimal for the system with certain and limited capacities a special case of which is the r q list price policy when capacities become unlimited as supply capacities become random the optimal policy follows a new structure wherein the optimal order up to level and posted price must be coordinated to make the optimal safety stock level follow the r q policy we further consider the case of a quasi convex cost rate function which may arise when a service level constraint is used as a surrogate for the shortage cost we demonstrate that the r q list price policy is optimal for the system without supply capacity constraints in addition extensions to several other models are discussed the enabling technique is based on the notion of q jump convexity and its variants

the effect of leadtime uncertainty in a simple stochastic inventory model we study a basic continuous time single item inventory model where demands form a compound poisson process and leadtimes are stochastic the performance measure of interest is the long run average cost order costs are linear so a base stock policy is optimal we focus on the behavior of the optimal base stock level in response to stochastically larger or more variable leadtimes we also investigate the behavior of the corresponding long run average costs we show that a stochastically larger leadtime requires a higher optimal base stock level however a stochastically larger leadtime may not necessarily result in a higher optimal average cost because sometimes the variability effects may dominate on the other hand a more variable leadtime always leads to a higher optimal average cost the effect of leadtime variability on optimal policies depends on the inventory cost structure a more variable leadtime requires a higher optimal base stock level if and only if the unit penalty holding cost rate is high low similar results regarding the effect of leadtime demand are also discussed in this latter case the compound poisson assumption is not necessary

technical note a note on the structure of joint inventory pricing control with leadtimes we consider a joint inventory pricing control problem for a periodic review single stage inventory system with a positive order leadtime and a linear order cost demands in consecutive periods are independent but their distributions depend on the price in accordance with a stochastic demand function of additive form pricing and ordering decisions are made simultaneously at the beginning of each period the objective is to maximize the total expected discounted profit over a finite horizon we partially characterize the structure of the optimal joint ordering and pricing policies we also show that our structural analysis can be extended to a multistage or serial inventory system with constant or stochastic leadtimes and an assemble to order system with price sensitive demand

schumpeter meeting keynes a policy friendly model of endogenous growth and business cycles this paper studies an agent based model that bridges keynesian theories of demandgeneration and schumpeterian theories of technology fueled economic growth we employ the model to investigate the properties of macroeconomic dynamics and the impact of public polices on supply demand and the fundamentals of the economy we find profound complementarities between factors influencing aggregate demand and drivers of technological change that affect both short run fluctuations and longterm growth patterns from a normative point of view simulations show a corresponding complementarity between keynesian and schumpeterian policies in sustaining long run growth paths characterized by milder fluctuations and relatively lower unemployment levels the matching or mismatching between innovative exploration of new technologies and the conditions of demand generation appear to suggest the presence of two distinct regimes of growth or absence thereof characterized by different short run fluctuations and unemployment levels

managing inventory with multiple products lags in delivery resource constraints and lost sales a mathematical programming approach this paper develops an order up tos inventory model that is designed to handle multiple items resource constraints lags in delivery and lost sales without sacrificing computational simplicity mild conditions are shown to ensure that the expected average holding cost and the expected average shortage cost are separable convex functions of the order up to levels we develop nonparametric estimates of these costs and use them in conjunction with linear programming to produce what is termed the lp policy the lp policy has two major advantages over traditional methods first it can be computed in complex environments such as the one described above and second it does not require an explicit functional form of demand something that is difficult to specify accurately in practice in two numerical experiments designed so that optimal policies could be computed the lp policy fared well differing from the optimal profit by an average of 2 20 and 1 84 respectively these results compare quite favorably with the errors incurred in traditional methods when a correctly specified distribution uses estimated parameters our findings support the effectiveness of this mathematical programming technique for approximating complex real world inventory control problems

information appropriability and the generation of innovative knowledge four decades after arrow and nelson an introduction this introduction sets in context the works that follow which are meant to take stock of the theoretical advances and also historical changes since the seminal arrow 1962 and nelson 1959 first we summarize some of the original arrow nelson insights second we map the subsequent developments shorthanded as the stanford yale sussex synthesis a particularly controversial issue concerns the relationships between notional opportunities of innovation private appropriability of return from innovating and realized rates of innovation hence third we briefly offer a framework for its discussion in general and with reference to the private appropriation of scientific knowledge copyright 2006 oxford university press

coordinating inventory control and pricing strategies for perishable products we analyze a joint pricing and inventory control problem for a perishable product with a fixed lifetime over a finite horizon in each period demand depends on the price of the current period plus an additive random term inventories can be intentionally disposed of and those that reach their lifetime have to be disposed of the objective is to find a joint pricing ordering and disposal policy to maximize the total expected discounted profit over the planning horizon taking into account linear ordering cost inventory holding and backlogging or lost sales penalty cost and disposal cost employing the concept of l concavity we show some monotonicity properties of the optimal policies our results shed new light on perishable inventory management and our approach provides a significantly simpler proof of a classical structural result in the literature moreover we identify bounds on the optimal order up to levels and develop an effective heuristic policy numerical results show that our heuristic policy performs well in both stationary and nonstationary settings finally we show that our approach also applies to models with random lifetimes and inventory rationing models with multiple demand classes

s s policies for a dynamic inventory model with stochastic lead times this study analyzes a stochastic lead time inventory model under the assumptions that a replenishment orders do not cross in time and b the lead time distribution for a given order is independent of the number and sizes of outstanding orders the study extends the existing literature on the finite horizon version of the model and yields an intuitively appealing dynamic program that is nearly identical to one that would apply in a transformed model with all lead times fixed at zero hence many results that have been derived for fixed lead time models generalize easily conditions for the optimality of myopic base stock policies and for the optimality of s s policies are established for both finite and infinite planning horizons the infinite horizon model analysis is extended by adapting the fixed lead time results for the efficient computation of optimal and approximately optimal s s policies

joint pricing procurement control under fluctuating raw material costs abstract we consider a firm that periodically procures raw material units stores them and processes them into finished products upon order arrivals the raw material cost evolves in a markovian fashion whereas the demand process is influenced by both the raw material cost and sales prices charged by the firm the firm controls both the raw material procurement activity and sales price in each period we show the optimality of base stock list price type of policies with the additional raw cost dependence under conditions that are verifiable when the firm engages in price competition with other firms tapping into the same raw material market and when the raw material cost process has time continuity and mean reversion tendencies we identify two monotone patterns in which policy parameters should follow as the raw material cost fluctuates cost increases are also shown to translate into price increases at low inventory levels in other circumstances however there does not appear to be a clear pattern as to how the firm should pass cost increases on to end customers our numerical evidence unequivocally supports the adaptation of procurement and pricing controls to changing raw material costs

empirical analysis of optimal strategic petroleum reserve in china abstract the chinese government began to prepare for the establishment of strategic petroleum reserve in march 2004 therefore answering the question of what level of strategic petroleum reserve would be suitable for china s future economic development becomes essential using a decision tree model based on a cost function this paper quantifies china s optimal strategic petroleum reserve for the period 2005 2020 this approach provides a methodology reference for further quantified discussion on china s spr our results show that for economic development and security of the energy supply the strategic petroleum reserve should be the equivalent of 30 60 days of net oil import for an optimal solution when the oil price is 50 bbl with a reserve of an equivalent of 60 90 days of net oil import to have an optimal solution when oil price is 20 35 bbl

r versus d estimating the differentiated effect of research and development on innovation results r d is considered to be the main source of innovation we argue that r d is too broad a measure including activities differing in purposes culture people management and other features however empirical studies have not analyzed them separately mainly due to the lack of data using firm level data the aim of this paper is to estimate the differentiated effect of research and development on different innovation outputs results show that both research and development activities are important however we find that development activities are more important for product innovation while the effect of research activities is higher on process innovation moreover we analyze differences by technological intensity of the sector when analyzing product and process innovations we find evidence supporting the existence of higher payoffs to development and especially to research in low tech sectors when compared with high tech ones