a hedonic travel cost analysis for valuation of multiple components of site quality the recreation value of forest management abstract one benefit of managing forests is that one can alter the qualities of sites the value of changing site qualities however is generally not known this paper develops a formal hedonic travel cost model which can be used to estimate the value of both marginal and non marginal changes to sites the approach accommodates multiple simultaneous changes in site characteristics estimating this model using a set of permits from wilderness areas leads to revealed preference estimates of the recreational value of clear cuts old growth and nine other wilderness attributes

the dual structure of incomplete demand systems integrability of incomplete demand systems is discussed the concepts of weak integrability quasi expenditure function quasi indirect utility function and quasi utility function are defined their relationships to the expenditure function indirect utility function and utility function are developed the dual structure of the quasi functions permits exact welfare analysis and reveals the conditional preference structure for the commodities of interest new results relating the uniqueness and exactness of consumer s surplus to the structure of the expenditure and indirect utility functions are obtained

separability partial demand systems and consumer s surplus measures abstract in practice complete demand systems are not estimated rather either an incomplete demand system is estimated or separability is invoked and a partial demand system is estimated this paper considers the relationship between the conventional compensating variation equivalent variation and the corresponding welfare measure that can be derived from a partial demand system and the current budget allocation to the separable group even assuming the separability assumption invoked is appropriate these partial measures provide in general only a limited amount of information about the compensating variation and no information about the equivalent variation great care is therefore needed when using partial welfare measures to evaluate policy

possibilities for including the opportunity cost of time in recreation demand systems recreation demand modelers have attempted to identify and incorporate the opportunity cost of an individual s time in travel and on site in the model larson 1993b focused on the value of leisure time in a model where individuals face a fixed work week in this paper we examine the connection between labor supply and recreation demands and focus on conditional demand systems we illustrate that corner solution models are not needed to explain several interesting time related recreation issues

estimating the cost of leisure time for recreation demand models abstract in this paper we propose a method of determining the opportunity cost of leisure time with an empirical recreation demand application typically the opportunity cost of leisure time is assumed to be some fraction of the wage rate this practice has limitations first it assumes that individuals can trade time for money at their wage second it offers no guidance about how to value the time of an individual who is not in the labor force this paper proposes a method of determining this cost that does not suffer from these drawbacks an empirical example is provided which demonstrates the proposed approach and contrasts it with commonly applied approaches

measuring the cost of time in recreation demand analysis comment in the february 1981 issue of the journal mcconnell and strand present a model of recreation demand in which the opportunity cost of an hour of travel to a recreation site is assumed not to equal the average hourly income of the recreating family they test the model with data from a 1978 survey of sportfishermen in the chesapeake bay region simply stated the model hypothesizes that the sportfishermen will behave as if the price of a recreational trip is the sum of cash costs and the opportunity cost of travel time this opportunity cost is hypothesized to be some ratio k of average family income per hour times the travel time mcconnell and strand estimate the value of k by regressing recreation days against cash costs and opportunity cost of time as separate variables the ratio of regression coefficients then is an estimate of k they go on to estimate the ratio k of the opportunity cost of travel to the average income for sportfishermen in the chesapeake bay region the authors hypothesize that the ratio k falls between 0 and 1 implying that sportfishermen value the time in transit lower than their average income when working sufficient conditions for k to equal one include a the tax rate is zero b marginal earnings are constant and c nonwork income equals zero this comment is written to point out certain aspects of the study which may have led to an underestimation of the value of k it is argued that mcconnell and strand have misspecified their demand equation in such a way that their estimate for k 612 is biased downward mcconnell and strand hypothesize the demand relation

optimal stationary policies in a 3 stage serial production distribution logistic chain facing constant and continuous demand in this paper we study a 3 stage production distribution system that faces constant and continuous demand the system is made up of three storing sites a production facility a warehouse and a retailer this system was constructed to study the need for coordinating distribution and production in the decision of lot sizes hence the production capacity is limited our objective is to compute lot sizes that leads to the lowest possible cost in such a system we consider stationary inventory management policies in such a policy a fixed lot size is supplied from one stage to the next with a constant time interval we introduce the concept of multiple policies and give a solution to find the best one we then prove that multiple policies are guaranteed to cost less than 1 51 more than the best stationary policy we improve this guarantee to 0 51 by adding some simple but non multiple policies to our candidate policies

modeling recreation demand in a poisson system of equations an analysis of the impact of international exchange rates we extend count data travel cost modeling by developing a utility theoretic system of semilogarithmic recreation demand equations the restrictions required to make the system utility theoretic are applied during estimation the model is applied to individual wilderness recreation trips in a system of four canadian wilderness parks the resulting demand system is used to examine the impacts of changing u s canadian currency exchange rates on participation and welfare of u s recreationists

coordinating a three level supply chain with learning based continuous improvement abstract learning curve theory has been widely used as a managerial tool to describe and model product and process improvement this paper investigates a three level supply chain supplier manufacturer retailer where the manufacturing operations undergo a learning based continuous improvement process improvements in the manufacturer s operation are characterized by enhanced capacity utilization reductions in set ups times and improved product quality through the elimination of rework as a result of these continuous improvements the manufacturer can justify a production policy that is based on more frequent smaller lot size production for this production policy to be practical and not sub optimal to the supply chain the manufacturer must integrate its lot sizing models with the replenishment policies of its upstream raw material suppliers and the demand requirements of its downstream customers retailers mathematical models that achieve chain wide lot sizing integration are developed and solution procedures for the models are illustrated by numerical examples the results demonstrate that learning based improvements in set up time and rework allow retailers to order in progressively smaller lot sizes as the manufacturer offers larger discounts and profits and that the entire supply chain benefits from implementing learning based continuous quality improvements the results also demonstrate that forgetting effects lead to increases in supply chain costs

a structural equations approach to modeling consumptive recreation demand abstract in this analysis we develop a two equation structural model of a count travel cost model of recreational angling demand and angling success by modeling the two equations jointly we avoid the difficulties associated with the usual approach which estimates the demand for recreational fishing sites assuming the existence of an exogenous measure of fishing quality our analysis explicitly develops the joint log likelihood function that combines the two processes we estimate our model using full information maximum likelihood methods

valuing time in travel cost demand analysis an empirical investigation the opportunity cost of time is usu ally a significant part of the price variable in the travel cost demand model thus its accurate mea surement is important to the estimation of demand and benefit valuation for nonmarket resources this paper empirically tests models which assume that income is the basis for opportunity time cost with an alternative pooled model based on a disequi librium labor market for some recreationists ac ceptance of the hypothesis that disequilibrium mod els may be necessary for some individuals implies increased survey information requirements so that the appropriate model can be applied to each indi vidual jel q21

integrated lot sizing in serial supply chains with production capacities we consider a model for a serial supply chain in which production inventory and transportation decisions are integrated in the presence of production capacities and concave cost functions the model we study generalizes the uncapacitated serial single item multilevel economic lot sizing model by adding stationary production capacities at the manufacturer level we present algorithms with a running time that is polynomial in the planning horizon when all cost functions are concave in addition we consider different transportation and inventory holding cost structures that yield improved running times inventory holding cost functions that are linear and transportation cost functions that are either linear or are concave with a fixed charge structure in the latter case we make the additional common and reasonable assumption that the variable transportation and inventory costs are such that holding inventories at higher levels in the supply chain is more attractive from a variable cost perspective while the running times of the algorithms are exponential in the number of levels in the supply chain in the general concave cost case the running times are remarkably insensitive to the number of levels for the other two cost structures

specification of driving costs in models of recreation demand existing recreation demand models have paid much attention to the heterogeneous nature of the opportunity cost of time but generally stipulate constant per mile costs in access price specifications this study proposes two alternative approaches to introduce user specific driving costs into recreation demand models the first approach is based on a refined measurement of driving costs based on engineering considerations the second strategy estimates perceived per mile cost as a function of vehicle attributes in an empirical framework we find strong evidence that driving costs are a visitor specific concept and that prescribed and perceived costs differ substantially however welfare measures generated by these alternative specifications are not statistically different from those produced by the standard model in our application of jet skiing in the lake tahoe region

specification considerations for the price variable in travel cost demand models the travel cost method tcm which is used to impute a value to outdoor recreation resources has traditionally examined the statistical relationship between visit rates to a site and the observed variable travel cost per visit users of the tcm then typically use that statistical relationship to infer a demand relation between visit rates and a schedule of unobserved entry fees in using data on these observed travel costs to infer a behavioral response to unobserved entry fees the tcm will only generate an unbiased estimate of consumer surplus accruing to site visitors in certain circumstances specifically assuming linearity it is required that the estimated linear coefficient bk explaining visits as a function of observed travel costs r f r is equal to the unobserved coefficient bp which explains visits as a function of entry fees price unfortunately nothing guarantees that bc is the same as bp thus in order to obtain an unbiased esti

coordinated supply chain management abstract historically the three fundamental stages of the supply chain procurement production and distribution have been managed independently buffered by large inventories increasing competitive pressures and market globalization are forcing firms to develop supply chains that can quickly respond to customer needs to remain competitive these firms must reduce operating costs while continuously improving customer service with recent advances in communications and information technology as well as a rapidly growing array of logistics options firms have an opportunity to reduce operating costs by coordinating the planning of these stages in this paper we review the literature addressing coordinated planning between two or more stages of the supply chain placing particular emphasis on models that would lend themselves to a total supply chain model finally we suggest directions for future research

time and the recreational demand model in this paper a theoretically consistent approach to including time costs in recreational demand models is developed the demand model is conditional on the recreationist s labor market situation for individuals at corner solutions in the labor market utility maximization is subject to two constraints leading to a demand function with travel costs and travel time as independent variables with interior solutions in the labor market time is valued at the wage rate and combined with travel costs to produce one full cost variable in an illustration welfare measures based on the new model are estimated for a sample of sportfishermen

searching for the opportunity cost of an individual s time a traditional assumption made in the literature is that the value of an individual s time spent in any activity is equal to his or her wage rate this result stems from the derivation of the value of leisure time in the context of the standard labor supply model this paper pre sents some reasons why the relationship be tween the wage rate and the value of time does not hold suggestions for what to do when the relationship breaks down and the investigator needs some value to impute to the individual are given in the final section of the paper

a latent class approach to modeling endogenous spatial sorting in zonal recreation demand models a method for incorporating unobserved heterogeneity into aggregate count data frameworks is presented and used to control for endogenous spatial sorting in zonal recreation models the method is based on latent class analysis which has become a popular tool for analyzing heterogeneous preferences with individual data but has not yet been applied to aggregate count data the method is tested using data on backcountry hikers for a southern california study site and performs well for relatively small numbers of classes the latent class model produces substantially smaller welfare estimates compared to a constrained version that assumes homogeneity throughout the population

a new approach to random utility modeling using the dirichlet multinomial distribution in this paper we introduce a new econometricapproach to analyzing recreational site choicedata the dirichlet multinomial model thismodel which nests the standard conditionalmultinomial logit model can accommodateover dispersed data and may provide moreefficient estimators of coefficients andconsequent welfare measures than the standardconditional logit model which is so widelyused in the random utility model approach torecreation demand we illustrate thisdirichlet approach using a data set of rockclimbers in scotland and study the impacts onper trip consumers surplus of alternativemanagement strategies for popular rock climbingsites results show that the dirichletmultinomial approach produces coefficient andwelfare estimates having smaller samplingvariability in this case we also compareclassical welfare measures with their posteriorequivalents which allow for welfare changes tobe dis aggregated

addressing aggregation bias in zonal recreation models abstract models of recreation demand are often based on zonal data results from such models are susceptible to aggregation bias we propose a zonal model of recreation that captures some of the underlying heterogeneity of individual visitors by incorporating distributional information on per capita income from census sources into the aggregate demand function this adjustment eliminates the unrealistic constraint of constant income across zonal residents and thus reduces the risk of aggregation bias in estimated parameters in addition the corrected aggregate specification reinstates the applicability of generalized maximum likelihood methods and increases model efficiency

measuring the cost of time in recreation demand analysis an application to sportfishing since the work of cesario and knetsch economists have recognized that the opportunity cost of time plays an important role in determining the demand for outdoor recreation the opportunities one has for spare time are more significant for consumption of time intensive outdoor recreation activities than for other commodities especially nondurables bishop and heberlein illustrate the overwhelming importance of time costs to final recreational values total consumer surplus is nearly four times as large when time costs are added at half the income rate as when time costs were set at zero p 21 despite the recognition economists have neither successfully integrated the costs of time with the methods of recreational demand analysis nor reached a consensus on how it should be measured brown charbonneau and hay state finally the apparently crucial importance of how opportunity cost of time is handled needs further work while we are convinced it is an appropriate concept exactly how it should be included and measured s remains to be determined p 24 several approaches have been taken to include it in the travel cost method one approach brown and nawas gum and martin suggests that time in transit be considered as a separate independent variable another approach bishop and heberlein brown charbonneau hay nicols bowes dwyer cesario and knetsch measures the cost of time and adds it to other costs several approaches have been suggested to measure time costs one approach is simply to choose an hourly wage e g 2 00 per hour or perhaps the minimum wage rate a more flexible but still ad hoc approach is to use some proportion of the individual s wage rate as the opportunity cost of time nichols bowes dwyer the proportion is usually taken from independent studies and used to value the travel time this approach is better than using a constant opportunity cost of time because it allows variation across individuals it suffers because the choice of the percentage of the wage rate is arbitrary independent of the sampled population cesario has discussed the consequences of ignoring time costs and the differences in values arising from alternative measurement approaches in this paper we argue that the opportunity cost of time is some proportion of the individual s market wage rate or income per hour and that this proportion can be determined from sample data this method permits the proportion to vary from one study to another rather than imposing either an arbitrary estimate or one from a sample different from the study s sample

recreation demand models with taste differences over people we estimate random parameter logit models of anglers choice of fishing site the models generalize logit by allowing coefficients to vary randomly over anglers rather than being fixed the models do not exhibit the restrictive independence from irrelevant alternatives property of logit and can represent any substitution pattern estimation explicitly accounts for the fact that the variation in coefficients over anglers induces correlation in unobserved utility over trips by the same angler willingness to pay for improved fish stock and the value to anglers of specific sites are calculated from the models and compared with the estimates obtained from a standard logit model

incorporating quantity discounts to the eoq model with transportation costs abstract this article extends a previous economic order quantity eoq model with two modes of transportation namely truckload tl and less than truckload ltl carriers by introducing all units and incremental quantity discount structures into the analysis exact algorithms are developed for each quantity discount structure to compute optimal policies for single stage models over an infinite planning horizon

lot sizing in a serial distribution system with capacitated in system production flow abstract in this paper we focus on an n stage serial production distribution system with limited production capacity at the first stage our objective in such a system is to find inventory management policies that minimize the global logistic cost including transportation and holding costs we use myopic heuristics based on the breakdown of the system into local systems one of these systems is a 2 stage system and the second is a 3 stage system they both can be solved with a very good performance guarantee the successive optimizations of such systems provide quite good policies for the global system as asserted by the experimental results at the end of the paper

a theoretical foundation for count data models the paper develops a theoretical foundation for using count data models in travel cost analysis two micro models are developed a restricted choice model and a repeated discrete choice model we show that both models lead to identical welfare measures

optimal production inventory policy for an integrated multi stage supply chain with time varying demand abstract an integrated multi stage supply chain with time varying demand over a finite planning horizon is considered in this paper the objective is to devise the optimal production inventory policy to minimize the total operational cost the model is formulated as a mixed integer nonlinear programming problem the problem is represented as a weighted directed acyclic graph the global minimum total operational cost is computed in polynomial time by the developed algorithm two numerical examples of a seasonal product and a product over its life cycle are studied to illustrate the results a sensitivity analysis of the system parameters is conducted to assist the supply chain decision makers

dynamic version of the economic lot size model this article originally appeared in management science october 1958 volume 5 number 1 pp 89 96 published by the institute of management sciences a forward algorithm for a solution to the following dynamic version of the economic lot size model is given allowing the possibility of demands for a single item inventory holding charges and setup costs to vary over n periods we desire a minimum total cost inventory management scheme which satisfies known demand in every period disjoint planning horizons are shown to be possible which eliminate the necessity of having data for the full n periods

modeling recreation demand in the presence of unobservable travel costs toward a travel price model an important issue in the application of travel cost models is the construction of a travel cost variable this paper develops an econometric approach that views travel costs as an unobserved latent variable the latent variable approach utilizes indicators to capture the role of individual travel costs in recreational demand models the latent variables approach has at least two advantages over conventional approaches one the indicators can include both traditional components such as time and distance and non traditional components such as the scenic beauty second the estimation procedure results in each indicator being valued in dollar terms

a smart market for industrial procurement with capacity constraints we address the problem of designing multi item procurement auctions for a monopsonistic buyer in capacity constrained environments using insights from classical auction theory we construct an optimization based auction mechanism smart market relying on the dynamic resolution of a linear program minimizing the buyer s cost under the suppliers capacity constraints suppliers can modify their offers in response to the optimal allocation corresponding to each set of bids giving rise to a dynamic competitive bidding process to assist suppliers we also develop a bidding suggestion device based on a myopic best response mbr calculation that solves an associated optimization problem assuming linear costs for the suppliers we study within a game theoretic framework the sequence of bids arising in this smart market under a weak behavioral assumption and some symmetry requirements an explicit upper bound for the winning bids is established we then formulate a complete behavioral model and solution methodology based on the mbr rationale and show that the bounds derived earlier continue to hold we analytically derive some structural and convergence properties of the mbr dynamics in the simplest nontrivial market environment which suggests further possible design improvements and investigate bidding dynamics and incentive compatibility issues via numerical simulations