research advances in environmentally and socially sustainable operations abstract consumers and governments are pressuring firms to strike a balance between profitability and sustainability however this balance can only be maintained in the long run if the firm can take a holistic approach to sustain the financial flow profit resource flow planet and development flow people for the entire ecosystem comprising poor producers in emerging developing markets global supply chain partners consumers in developed countries and the planet by considering the flows associated with different entities within the ecosystem we classify and summarize recent operations research management science or ms research developments also we identify several gaps for future research in this important area

peacock and wiseman on the growth of public expenditure the late nineteenth century view of the growth of the public sector enuciated by adolph wagner 1890 now known as wagner s law accorded well with the doctrine of comparative advantage with the growth of the industrial economy a complementary demand was set up alongside industrial and manufacturing expansion for transport and communication services energy and waste disposal central and local governments were viewed as having a comparative advantage in providing such services justifying wagner s law that government expenditure would continuously increase as a percentage of gross domestic product in a growing economy in 1961 as part of their seminal study of the growth of public expenditure in the united kingdom alan t peacock and jack wiseman1 questioned the generality of wagner s law and introduced their now famous displacement effect hypothesis to explain the time path of the growth of government in democratic countries writing before the public choice research program was at all well established peacock and wiseman nevertheless rejected wagner s reliance upon the organic state and relied instead on political propositions that

firm incentives to promote technological change in pollution control reply abstract the process of technological change in pollution control is broken into three basic steps innovation diffusion and optimal agency response firm incentives to promote these steps are then examined under five regulatory regimes direct controls emission subsidies emission taxes free marketable permits and auctioned marketable permits on a relative basis emission taxes and auctioned permits provide the highest firm incentives to promote technological change at times free permits generate lower incentives direct controls which are common regulatory tools usually provide the lowest relative firm incentives to promote technological change

international pollution control cooperative versus noncooperative strategies abstract international pollution control involving two neighboring countries is modeled as a simple two player dynamic game each country produces a good that is consumed by domestic households production of each consumption good results in emissions of pollutants households in each country derive utility from the consumption of the domestically produced good but incur costs through the total stock of pollution stock externality in this setting we characterize cooperative as well as noncooperative pollution control strategies of the governments of the two countries that maximize the discounted stream of net benefits of a representative consumer it turns out that when the governments are restricted to use linear strategies noncooperative behavior results in overall losses for both countries if on the contrary governments use nonlinear markov perfect strategies and the discount rate is small enough a pareto efficient steady state pollution stock can be supported as a differentiable subgame perfect equilibrium thus the emergence of first best solutions cooperative outcomes does not require any institutional arrangements threats retaliation etc but can be brought about through the use of nonlinear markov perfect equilibrium strategies

valuing the beneficts of air pollution abatement using a health production function a case study of panipat thermal power station india the indian economy today is highly prone to industrial pollution and ismaking compliance decisions in order to meet environmental standards environmental regulations impose significant costs upon industry that arefairly high and therefore require economic justification this justificationcan be given by estimating the benefits associated with these costs whilethe scientific rationale behind air quality preservation is well understood its economic rationale for a developing country like india has to beverified the objective of the present paper is to estimate the economicvalue that people in an urban area in india panipat thermal power station ptps colony in panipat haryana place upon improving the air quality the dose response method based on the gerking and stanley 1986 model is used to estimate the economic benefits of air quality improvement theseestimates range from one to two percent of monthly income income andhealth status variables were significant determinants of peoples willingness to pay wtp for air quality improvements this lends supportto the neo conventional wisdom act now to protect the environment beforeit is too late these people are ready to pay for environmentalimprovements we do believe however that the relatively successfulapplication of the dose response method at ptps colony suggests that thetechnique can be more widely applied in developing countries like india

the development of the new monetary economics this paper looks into the history of economic thought to examine the forerunners of the new monetary economics this approach emphasizes the role of regulations on private financial intermediation in determining the particular institutional arrangements that contemporary monetary theory treats as data the new view investigates the possibility that under laissez faire the unit of account and means of payment traditionally bundled together in the item called money may become separated the earlier writers who share this perspective have been overlooked by historians of economic thought as well as by recent contributors to the new monetary economics an examination of these theorists is of more than historical interest for many of their insights and analyses are relevant to modern monetary theory

measurement error and state dependent pollution control enforcement abstract a two group model of state dependent enforcement is applied to identical firms which minimize the expected present value of costs and fines measurement error affects the probabilities of transitions between groups and the receipt of fines it is shown that state dependent enforcement can reduce social cost below the level attainable with static enforcement and that differentiation in both monitoring probabilities and standards may be optimal however setting fines for both groups at the maximum is likely to be optimal comparisons between models and alternative model interpretations are offered

strategic response to pollution taxes in supply chain networks dynamic spatial and organizational dimensions abstract this paper presents a model of the strategic behavior of firms operating in a spatial supply chain network the manufacturing and retailing firms engage in an oligopolistic noncooperative game by sharing customer demand such that a firm s decisions impact the product prices which in turn result in changes in all other firms decisions each firm s payoff is to maximize its own profit and we show that in response to such changes in prices and to exogenous environmental taxes the manufacturing firms may strategically alter a variety of choices such as make buy decisions with respect to intermediate inputs spatial distribution of production product shipment patterns and inventory management environmental tax payment vs recycling decisions and timing of all such choices to sustainably manage the profit and the environmental regulations an important implication is that effects of a tax depends on the oligopolistic game structure with respect to methods we show that this dynamic game can be represented as a set of differential variational inequalities dvis that motivate a computationally efficient nonlinear complementarity ncp approach that enables the full exploitation of above mentioned salient features we also provide a numerical example that confirms the utility of our proposed framework and shows substantial strategic reaction can be expected to a tax on pollution stocks

the economics of cooperation over collective bads abstract pollution reciprocated among nations is analyzed graphically as a traded collective bad the model is contrasted to analogous methods of studying trade in public goods the model then is interpreted in terms of pollution taxes equilibrium and optimal outcomes are characterized by the tax policies needed to support them finally obstacles to tax trade solutions are noted and institutional solutions are suggested

optimal pricing and advertising in a durable good duopoly abstract this paper analyzes dynamic advertising and pricing policies in a durable good duopoly the proposed infinite horizon model while general enough to capture dynamic price and advertising interactions in a competitive setting also permits closed form solutions we use differential game theory to analyze two different demand specifications linear demand and isoelastic demand for symmetric and asymmetric competitors we find that the optimal price is constant and does not vary with cumulative sales while the optimal advertising is decreasing with cumulative sales comparative statics for the results are presented

revenue sharing in airline alliances we propose a two stage game theoretic approach to study the operations of an airline alliance in which independent carriers managing different reservation and information systems can collaboratively market and operate codeshare and interline itineraries in the first stage game airlines negotiate fixed proration rates to share the revenues generated by such itineraries in the second stage game airlines operate independent inventory control systems to maximize their own expected revenues we derive a revenue sharing rule that is i an admissible outcome of the first stage negotiation in the sense that no airline coalition has enough incentives to secede from the grand alliance and ii efficient for the second stage game in the sense that the decentralized system can achieve the same revenues as a central planner managing the global alliance network our numerical study shows that the proposed proration rates can lead to a significant increase in revenues with respect to other rules commonly used

carbon capture and storage and transboundary pollution a differential game approach abstract we study the strategic behavior of two countries facing transboundary co2 pollution under a differential game setting in our model the reduction of co2 concentration occurs through the carbon capture and storage process rather than through the adoption of cleaner technologies furthermore we first provide the explicit short run dynamics for this dynamic game with symmetric open loop and a special markovian nash strategy then we compare these strategies at the games steady states and along some balanced growth paths our results show that if the initial level of co2 is relatively high state dependent emissions reductions can lead to higher overall environmental quality hence feedback strategy leads to less social waste

the curious attraction of wagner s law wagner s law of increasing state activity has recently been subjected to intensive use of recondite econometric testing procedures an examination of the relevant articles reveals ignorance both of wagner s definition of state activity and of his insistence that he was not engaged in prediction consequently the omission of public enterprises contained in wagner s definition leads to a model misspecification and the object of testing his hypothesiss remains obscure

persistence in government spending fluctuations new evidence on the displacement effect in spite of peacock and wiseman s 1961 nber study demonstrating the displacement effect simplistic theoretical and empirical distinctions between temporary and permanent spending are common in this paper impulse response functions from arma models as well as cochrane s non parametric method support peacock and wiseman s conclusion by showing 1 government spending in the aggregate displays strong persistence to temporary shocks 2 simple decomposition methods intended to yield a temporary spending series have a weak statitistical foundation and 3 persistence in spending has increased during this century also as a basic fact of government spending behavior the displacement effect lends support to interest group and bureaucracy models of government spending growth

the mechanics of indirect convertibility this paper sets out the mechanics and equilibrating processes of indirectly convertible monetary systems in which currency issuing banks redeem their currency with redemption media of the same value as the commodity or commodity basket that defines the dollar it goes on to investigate the paradox of indirect convertibility and suggests that indirect convertibility is feasible despite the paradox finally it assesses the systems of fisher hall and others that have been suggested as alternatives to indirect convertibility but concludes that these alternative systems are open to serious objections copyright 1995 by ohio state university press

pollution accumulation and abatement policy in a supply chain abstract this paper seeks to determine how the double marginalization phenomenon affects the tradeoff between polluting emissions and abatement activities related to pollution accumulation in a supply chain composed of one manufacturer and one retailer the environmental consequence of this inefficiency which emerges in a non cooperative vertical setting governed by a single parameter contract is overlooked in the literature on pollution control in the setup of a two stage game we investigate the impact of double marginalization for non cooperative equilibrium to check whether there are differences between dynamic and strategic effects of double marginalization on pollution accumulation both the open loop and feedback nash equilibria are derived over a finite time horizon with the cooperative solution as a benchmark

are there limits to growth a simple theoretical model of pollution is developed that generates an inverted u shape relationship between per capita income and environmental quality this model is then used to study long run growth the same inverted u shape is shown to appear in time series and the prospects for sustained growth are shown to hinge on whether increasingly strict environmental regulation is compatible with a constant rate of return on capital implementation is also studied tax and voucher schemes are shown to have an advantage over direct regulation because they provide the correct incentives for capital accumulation copyright 1998 by economics department of the university of pennsylvania and the osaka university institute of social and economic research association

emissions trading electricity restructuring and investment in pollution abatement this paper analyzes an emissions trading program that was introduced to reduce smog causing pollution from large stationary sources using variation in state level electricity industry restructuring activity i identify the effect of economic regulation on pollution permit market outcomes there are two main findings first deregulated plants in restructured electricity markets were less likely to adopt more capital intensive environmental compliance options as compared to regulated or publicly owned plants second as a consequence of heterogeneity in electricity market regulations a larger share of the permitted pollution is being emitted in states where air quality problems tend to be more severe jel l51 l94 l98 q53 q58 when the us federal government first began regulating major sources of air pollution in the 1960s the conventional approach to meeting air quality standards involved establishing maxi mum emissions rates or technology based standards for regulated stationary sources however economists have long maintained that an emissions permit market could more efficiently coor dinate pollution abatement activities provided a series of assumptions are met over the past few decades market based cap and trade cat approaches to regulating emissions from industrial point sources have become a centerpiece of environmental regulation in the united states in the theoretical first best permit market equilibrium the total social cost of meeting an emis sions cap is minimized each firm chooses a level of pollution abatement such that its marginal cost of reducing pollution is set equal to the social marginal benefit from emissions reduction in practice preexisting distortions in product markets that are subject to cat regulation may interfere with the emissions permit market s ability to operate efficiently this paper studies the effects of electricity market regulation on permit market outcomes in the context of a major us emissions trading program the nox budget program the recent wave of electricity industry restructuring in the united states has resulted in significant interstate variation in economic regulation consequently facilities in the same cat program face very different economic regu lation and investment incentives in their respective electricity markets whereas rate base regu lated plants are guaranteed to earn a rate of return on prudent investments in pollution abatement equipment deregulated plants operating in restructured electricity markets are offered no such

the displacement effect in the growth of governments we analyze the displacement effect within a multivariaterevenue expenditure model of government growth based on along historical dataset for italy our long run analysisshows a permanent influence of domestic product on the growthof governments supporting wagner s law the short rundynamics are more complex and provide some evidence for thedisplacement effect in terms of a lower resistance againsttax financing of government spending in the post war inaddition government spending adjusts faster when deviationsfrom its equilibrium get larger

a laissez faire approach to monetary stability this paper develops some diverse hints for a new monetary system offered separately by fischer black eugene fama and robert e hall for reasons that will become evident though we should perhaps say payments system instead of monetary system none of the economists mentioned has actually proposed the particular system set forth here nor examined all its properties and we call it the bfh system not to implicate them but only to give credit for some component ideas and to have a convenient label l regardless of who if anyone may actually advocate the system contemplating it is instructive it illuminates by contrast some characteristics of our existing and recent systems

a monopolistic and oligopolistic stochastic flow revenue management model this paper studies a one shot inventory replenishment problem with dynamic pricing the customer arrival rate is assumed to follow a geometric brownian motion homogeneous customers have an isoelastic demand function and do not behave strategically we find a closed form optimal pricing policy which utilizes current demand information under this pricing policy the inventory trajectory is deterministic and a retailer sells all inventory we show that dynamic pricing coordinated with the inventory decision achieves significantly higher profits than does static pricing furthermore under oligopolistic competition we establish a weak perfect bayesian equilibrium for the price and inventory replenishment game we find the pricing equilibrium to be cooperative even in a noncooperative environment but that inventory competition results in overstock and damages profits finally we examine the trade off between dynamic pricing and price precommitment and find that flexible pricing is still beneficial provided competition is not too intense

irving fisher and price level targeting in austria was silver the answer the question of price level versus inflation targeting remains controversial disagreement concerns not so much the desirability of price stability but rather the means of achieving it irving fisher argued for a commodity dollar standard where the purchasing power of money was fixed by indexing it to a basket of commodities we show that movements in the price of silver closely track the movements in overall prices during the classical gold standard era the one to one relationship between paper and silver bonds suggests that a simple silver rule could have sufficed to fix the purchasing power of money

economic development and environmental quality a reassessment in light of nature s self regeneration capacity abstract we study the relationship between economic development and consumption of natural resources using a vintage capital model consumption of natural resources is assumed to generate pollution part of which will be absorbed by nature s self regeneration capacity we find that during the transition dynamics the shape of the pollution output relationship will depend on the parameter determining nature s self regeneration capacity using footprint and biological capacity data we show empirically in a repeated cross section of countries that the shape of the pollution output relationship indeed depends on countries capacity to regenerate part of the resources they consume from nature

the impact of environmental management on firm performance environmental management has the potential to play a pivotal role in the financial performance of the firm many individuals suggest that profitability is hurt by the higher production costs of environmental management initiatives while others cite anecdotal evidence of increased profitability a theoretical model is proposed that links strong environmental management to improved perceived future financial performance as measured by stock market performance the linkage to firm performance is tested empirically using financial event methodology and archival data of firm level environmental and financial performance significant positive returns were measured for strong environmental management as indicated by environmental performance awards and significant negative returns were measured for weak environmental management as indicated by environmental crises the implicit financial market valuation of these events also was estimated cross sectional analysis of the environmental award events revealed differences for first time awards and between industries first time award announcements were associated with greater increases in market valuation although smaller increases were observed for firms in environmentally dirty industries possibly indicative of market skepticism this linkage between environmental management and financial performance can be used by both researchers and practitioners as one measure of the benefits experienced by industry leaders and as one criterion against which to measure investment alternatives

emission path planning based on dynamic abatement cost curve abstract global climate change is one of the most serious environmental problems that has attracted an unprecedented global attention the scientific community has recognized that human activity is mostly responsible for global climate warming therefore states participating in the united nations framework convention on climate change unfccc have initiated a series of negotiations on how to develop their own emission reduction targets however the realization of these targets is at the expense of economic development to a great extent therefore an abatement plan is necessary to decide how and when to implement emission reduction targets a marginal abatement cost curve macc often used as an important quantitative tool to estimate abatement burden or evaluate abatement performance should be considered carefully in this paper we enrich the traditional macc by introducing the concept of an immediate unit marginal abatement cost to describe its intrinsic incremental abatement difficulty this cost is proved to be agreed with the actual situation in many ways and is therefore very suitable for practical use two factor learning curve are considered in the model which can go some way in improving the performance of the revised macc using a parameterization method the original problem can be converted into a tractable nonlinear programming problem we use an algorithm to search for the approximate global optimal solution the effectiveness and the efficiency of the algorithm are discussed respectively in the results we find that the abatement path distinguishes largely under different abatement targets some plausible reasons and policy advices are given

the impact of foresight in a transboundary pollution game abstract we study the impact of foresight in a transboundary pollution game i e the ability of a country to control its emissions taking into account the relationship between current emissions and future levels of pollution and thus on future damages we show that when all countries are myopic i e choose the laisser faire policy their payoffs are smaller than when all countries are farsighted i e non myopic however in the case where one myopic country becomes farsighted we show that the welfare impact of foresight on that country is ambiguous foresight may be welfare reducing for the country that acquires it this is due to the reaction of the other farsighted countries to that country s acquisition of foresight the country that acquires foresight reduces its emissions while the other farsighted countries extend their emissions the overall impact on total emissions is ambiguous moreover our results suggest that incentive mechanisms that involve a very small possibly zero present value of transfers can play an important role in inducing a country to adopt a farsighted behavior and diminishing the number of myopic countries these incentives would compensate the myopic country for the short run losses incurred from the acquisition of foresight and can be reimbursed by that country from the gains from foresight that it enjoys in the long run

emission permit banking pollution abatement and production inventory control of the firm abstract in this paper we present a dynamic model modified with emission permit banking and pollution abatement and investigate the effect of emission permit banking and pollution abatement on the production inventory strategy of the firm after introducing emission permit banking and pollution abatement the cost function consists of the inventory holding and production costs the cost of investment in abatement capital goods and the emission procurement selling cost furthermore the inventory holding costs are linear production costs are non decreasing and convex functions of the production level and the costs of investment in abatement capital goods are increasing and convex functions of the investment level we compare the optimal production inventory strategy before emission permit banking and pollution abatement and thereafter the mathematical investigation is based on the arrow karlin model

dynamics of supply chain networks with corporate social responsibility through integrated environmental decision making in this paper we develop a dynamic framework for the modeling and analysis of supply chain networks with corporate social responsibility through integrated environmental decision making through a multilevel supply chain network we model the multicriteria decision making behavior of the various decision makers manufacturers retailers and consumers which includes the maximization of profit the minimization of emission waste and the minimization of risk we explore the dynamic evolution of the product flows the associated product prices as well as the levels of social responsibility activities on the network until an equilibrium pattern is achieved we provide some qualitative properties of the dynamic trajectories under suitable assumptions and propose a discrete time algorithm which is then applied to track the evolution of the levels of social responsibility activities product flows and prices over time we illustrate the model and computational procedure with several numerical examples

technological innovation and green growth in the organization for economic cooperation and development economies abstract green growth means improving production and demand based emissions through innovation of green technologies for cleaner production and supply chain this study examines the effect of technological innovation on green growth on twenty eight 28 organization for economic cooperation and development oecd economies for the period 2000 to 2014 with data sourced from oecd library statistics and world bank world development indicators the economies were sub grouped into oceania america asia and europe preliminary tests conducted were cross section dependence test im pesaran and shin unit root tests westerlund cointegration confirmed that the variables are cointegrated using stirpat and ipat models the study found transport related technologies has been beneficial to green growth in the oceania sub region oecd asia s technologies for production and processing of goods have been beneficial to green growth climate change technologies in relation to generation and transmission of energy are detrimental to green growth in the oecd economies but its impact is visible in asia and europe sub panels environmental related budget and taxes have been found worthwhile in the pursuit of green growth from the dominant negative coefficient values findings led to the presentation of some important implications which could be useful for policy makers and industries in the pursuit of green growth globally

incentives for advanced pollution abatement technology at the industry level an evaluation of policy alternatives abstract in this research we evaluate the incentive effects of five environmental policy instruments to promote the development and adoption of advanced pollution abatement technology in a heterogenous industry from most to least incentive the policy instruments can be rank ordered as follows i auctioned permits ii emissions taxes and subsidies iii issued marketable permits iv performance standards including performance standards in this list necessitates the assumption that they are differentiated between heterogeneous firms before the technology adoption in a way which replicates the initial emissions control distribution of the efficient incentive based instruments with the starting point normalized in this fashion the instrument rankings are invariant with respect to the size of firms the size of the industry or the industry s abatement cost structure

existence and properties of equilibria for a dynamic game on productive assets abstract we consider a model in which two agents share access to the same stock of a productive asset and study the implications of non cooperative consumption behavior over time under standard assumptions on the production function we construct infinitely many nash equilibria all of which consist of stationary markovian strategies these equilibria result in overconsumption so that the uniquely determined long run asset stock is too low as compared to the cooperative solution however in the limit as the discount rate becomes sufficiently small the stead states generated by the markovian nash equilibria converge to the efficient steady state journal of economic literatureclassification numbers c73 o41 q22

competition in multiechelon assembly supply chains in this paper we study competition in multiechelon supply chains with an assembly structure firms in the supply chain are grouped into homogenous sectors nodes that contain identical firms with identical production capabilities that all produce exactly one undifferentiated product that may itself be a kit of components each sector may use several inputs to produce its product and these inputs are supplied by different sectors the production process within any sector is taken to be pure assembly in fixed proportions the number of firms in each sector is known the demand curve for the final product is assumed to be linear as are production costs in all sectors competition is modeled via a coordinated successive cournot model in which firms choose production quantities for their downstream market so as to maximize profits given prices for all inputs and all complementary products production quantities for sectors supplying the same successor are coordinated through pricing mechanisms so that complementary products are produced in the right proportions under these assumptions equilibrium prices for any multiechelon assembly network are characterized by a system of linear equations we derive closed form expressions for equilibrium quantities and prices in any two stage system i e a system with multiple input sectors and a single assembly sector we show that any assembly structure can be converted to an equivalent larger structure in which no more than two components are assembled at any node finally large structures can be solved either by direct solution of the characteristic linear equations or through an iterative reduction compression to smaller structures

the forerunners of new monetary economics proposals to stabilize the unit of account note this paper critically evaluates the monetary policy regimes proposed by arthur kitson 1917 and henry meulen 1934 contrary to the assertion of tyler cowen and randall kroszner 1987 the unit of account envisioned by these earlier theorists was not at all like recent proposals by proponents of the new monetary economics it is also demonstrated that the compensated dollar plans of aneurin williams 1892 and irving fisher 1920 are closer forerunners to the recent new monetary economics proposals copyright 1990 by ohio state university press

the dynamics of lobbying a differential game this paper presents a dynamic model on lobbying the interactions between two competing lobbies who attempt to influence regulations and legislation are modelled as a differential game we consider for this game first a time consistent and then a subgame perfect equilibrium in linear markov strategies the subgame perfect equilibrium lowers considerably lobbying activity and expenses this provides a partial explanation of the puzzle that rent seeking expenses are often small compared with the prize sought

optimal control for transboundary pollution under ecological compensation a stochastic differential game approach abstract to account for previously ignored yet widely observed uncertainty in nature s capability to replenish the natural environment in ways that should inform ideal design of ecological compensation ec regimes this study constructs a stochastic differential game sdg model to analyze transboundary pollution control options between a compensating and compensated region equilibrium strategies in the stochastic two player game inform optimal control theory and reveal a welfare distribution mechanism to form the basis of an improved cooperative game contract a case based numerical example serves to verify the theoretical results and supports three key insights first accounting for various random disturbance factors the probabilistic pollutant stock in stackelberg non cooperative game exceeds that of a cooperative game situation second the ec mechanism provides long term effective incentives only when the marginal losses of environmental damage in the compensating region are more than twice that of the compensated region achieving a pareto optimal equilibrium relies upon the attainment of a dynamic allocation ratio derived from the analysis of a robust welfare allocation mechanism third cross region cooperation reliably outperforms stackelberg non cooperation due to either overwhelming incumbent economic interests or high abatement costs this study illuminates the importance of balancing both parties interests within an ec agreement while reducing uncertainty around unobserved environmental factors during ex ante negotiations

monetarist rules in the light of recent experience recent experience does not include a monetarist experiment as some have argued but may slightly reinforce preexisting reasons for doubting that the best way of formulating monetarist policy prescriptions is in the form of a constant growth rule for the money stock a more desirable rule would pertain to the monetary base which is much more directly under fed control while a constant base growth rule might provide good macroeconomic performance better results should be obtainable from a rule that at regular intervals adjusts the base growth rate upward or downward depending on whether nominal gnp is below or above a target path that specifies constant non inflationary growth for that variable this type of rule is activist to an extent but is non discretionary the implied absence of policy making flexibility is desirable for reasons explained in the literature on dynamic inconsistency this abstract was borrowed from another version of this item