intertemporal cost dependence in the presence of managerial impatience abstract a multi period agency problem arising in the presence of intertemporal cost dependence is investigated the principal delegates production decisions to a manager who is impatient the manager has private information on the nature of cost dependence that takes the form of an experience effect since the impatient manager would not invest enough to gain experience the principal designs a second best scheme to motivate the manager to increase intertemporal profit for the firm the second best scheme is obtained as a direct revelation mechanism that specifies outputs prices as well as the manager s compensation a significant result is that unlike the first best case impatience is not necessarily a disadvantage with asymmetric information impatience can be exploited to reduce the manager s information rent resulting in preferred outcomes for the principal

can economics be founded on indisputable facts of experience lionel robbins and the pioneers of neoclassical economics robbins argues that the fundamental propositions of microeconomic theory are deductions from the assumption that individuals act on consistent preferences this indisputable fact of experience does not need to be validated in controlled experiments while recognising that some neoclassical pioneers based the theory on psychological hedonism robbins claims that his own approach of pure theory belongs to a parallel and sounder tradition exemplified by menger and wicksteed this paper argues that robbins methodological defence of pure theory is incoherent and that his claim to find an intellectual lineage in the works of menger and wicksteed overlooks important discontinuities

optimal investment in learning curve technologies we study optimal investment in technologies characterized by the learning curve there are two investment patterns depending on the shape of the learning curve if the learning process is slow firms invest relatively late and on a larger scale if the curve is steep firms invest earlier and on a smaller scale we further demonstrate that learning investment differs greatly from investment in technologies without learning effects learning investments generate substantial initial losses and are very sensitive to downside risk we show that the most susceptible to losses and risk are technologies with intermediate speed of learning

cost externalities and corporate diversification abstract this paper examines the optimal time of entry by established firms that strategically exploit cost externalities resulting from experience transfer from their core product line to the entered market established firms may delay entry even under conditions when newborn firms would enter early the paper can also explain other entry scenarios including early diversification at an initial loss into markets that newborn firms would never enter the shape of the experience curve in the entered market strongly affects these differences in scenarios

the generalized multinomial logit model accounting for scale and coefficient heterogeneity the mixed or heterogeneous multinomial logit mixl model has become popular in a number of fields especially marketing health economics and industrial organization in most applications of the model the vector of consumer utility weights on product attributes is assumed to have a multivariate normal mvn distribution in the population thus some consumers care more about some attributes than others and the iia property of multinomial logit mnl is avoided i e segments of consumers will tend to switch among the subset of brands that possess their most valued attributes the mixl model is also appealing because it is relatively easy to estimate recently however some researchers have argued that the mvn is a poor choice for modelling taste heterogeneity they argue that much of the heterogeneity in attribute weights is accounted for by a pure scale effect i e across consumers all attribute weights are scaled up or down in tandem this implies that choice behaviour is simply more random for some consumers than others i e holding attribute coefficients fixed the scale of their error term is greater this leads to a scale heterogeneity mnl model s mnl here we develop a generalized multinomial logit model g mnl that nests s mnl and mixl by estimating the s mnl mixl and g mnl models on 10 data sets we provide evidence on their relative performance we find that models that account for scale heterogeneity i e g mnl or s mnl are preferred to mixl by the bayes and consistent akaike information criteria in all 10 data sets accounting for scale heterogeneity enables one to account for extreme consumers who exhibit nearly lexicographic preferences as well as consumers who exhibit very random behaviour in a sense we formalize below

real options analysis of investment in solar vs wind energy diversification strategies under uncertain prices and costs in this paper we study a community or firm considering to diversify its investment in two distinct renewable energy technologies namely wind and solar pv electricity we assume technological learning curves as a function of cumulative capital investment a real options approach is applied as it takes into account uncertainty about prices and learning as well as irreversibility associated with investment decisions we investigate three different cases dealing with uncertainty about future electricity prices and uncertainty about the speed with which learning drives the costs of wind and solar electricity down we assess the minimum threshold for the stochastic price and the maximum electricity production cost that makes it optimal for the firm to invest in the two technologies the results show that the learning rate affects the option to invest in but reducing critical threshold for exercising it the greater the amount of capital invested the more learning stimulates earlier exercising of the option to invest the firm will then anticipate the option to invest and exercise it for lower critical threshold values if all capital is invested in one technology if capital investment is diversified the option should be exercised at a higher critical threshold more uncertainty in energy prices or technology costs postpones the option to invest although investing in both solar and wind may be profitable under particular conditions of price and cost uncertainty the theoretically optimal strategy is generally investing in only one technology that is solar or wind depending on their relative initial costs and learning rates this suggests that the practice in most countries of diversifying renewable energy may reflect a mistaken strategy

preferences for mitigation of the negative impacts of the oil and gas industry in the niger delta region of nigeria we examine nigerian preferences for the mitigation of negative impacts associated with oil and gas production using a discrete choice experiment we analyse the data using a bayesian infinite mixtures model which given its flexibility can approximate an array of existing model specifications including the mixed logit and finite mixture specifications the application of this model to our data suggest multimodality in the marginal willingness to pay distributions associated with mitigation policy characteristics individuals are willing to pay for mitigation of negative impacts but are not necessarily willing to trade off very large increases in unemployment or poverty to achieve these benefits

optimizing the level of renewable electric r d expenditures using real options analysis abstract one of the primary objectives of the united states federal non hydro renewable electric r d program is to promote the development of technologies that have the potential to provide consumers with stable and secure energy supplies in order to quantify the benefits provided by continued federal renewable electric r d this paper uses real option pricing techniques to estimate the value of renewable electric technologies in the face of uncertain fossil fuel prices within the real options analysis framework the current value of expected future supply from renewable electric technologies net of federal r d expenditures is estimated to be 30 6 billion of this value 86 can be attributed to past federal r d efforts and 14 can be attributed to future federal r d efforts assuming continued federal r d funding at 300 million yr in addition real options analysis shows that the value of renewable electric technologies increases as current and future r d funding levels increase this indicates that the current level of federal renewable electric r d funding is sub optimal

does altruism undermine existence value abstract the debate over the use of contingent valuation for existence values or passive use values has failed to explore the validity of motives for such values one potential motive altruism has conflicting implications for benefit cost analysis depending on whether the altruist is paternalistic this paper constructs models of three types of altruism and shows how benefit cost analysis responds to each type of altruism how damage assessment and restoration depend on each type and the implications of a population of heterogeneous altruists

a real options approach to labour shifts planning under different service level targets abstract firms that experience uncertainty in demand as well as challenging service levels face among other things the problem of managing employee shift numbers decisions regarding shift numbers often involve significant expansions or reductions in capacity in response to changes in demand in this paper we quantify the impact of treating shifts in workforce expansion as investments while considering required service level improvements the decision to increase shifts whether by employing temporary workers or hiring permanent employees is one that involves significant risks traditional theories typically consider reversible investments and thus do not capture the idiosyncrasies involved in shift management in which costs are not fully reversible in our study by using real options theory we quantify managers ability to consider this irreversibility aiming to enable them to make shift decisions under conditions of uncertainty with the maximum level of flexibility our model aims to help managers make more accurate decisions with regard to shift expansion under service level targets and to defer commitment until future uncertainties can be at least partially resolved overall our investigation contributes to studies on the time required to introduce labour shift changes while keeping the value of service level improvements in mind

participatory environmental education and willingness to pay for river basin management empirical evidence from nigeria this paper examines the role of participation as a tool for improving individuals perceptions and environmental values using a test retest experiment conducted in south eastern nigeria two identical contingent valuation experiments were interspersed by participatory workshops designed to involve respondents in framing and forming the valuation scenario econometric analyses found that participatory education significantly developed individuals perceptions of pollution problems and increased the magnitude and precision of their wtp for a river basin management scheme the extent of changes in perceptions declined with increasing levels of formal education suggesting that less educated respondents are more likely to hold weakly formed preferences

a theorist s view of experiments the paper springs from a position that economic theory is an abstract investigation of the concepts and considerations involved in real life economic decision making rather than a tool for predicting or describing real behavior it is argued that when experimental economics is motivated by theory it should not look to verify the predictions of theory but instead should focus on verifying that the considerations contained in the economic model are sound and in common use it is argued that when theory is motivated by experiments the theorist should not be hasty in adopting new functional forms but should try to identify the basic psychological themes which are revealed exposed by the experiment finally some critical comments on the methodology of experimental economics are presented 2001 elsevier science b v all rights reserved jel classi cation b0 c9

the learning curve market dominance and predatory pricing sufficient conditions for id and iid are given in the case of two step learning in which a firm reaches the bottom of its learning curve after just two sales however examples are also constructed for the two step learning case in which neither id nor iid holds it is also shown that in equilibrium iid implies that learning is privately disadvantageous although it is socially advantageous finally introducing avoidable fixed costs and possible exit into the model yields a new theory of predatory pricing based on the learning curve hypothesis

learning by doing and product durability many durable goods industries are industries that have significant learning affects i examine a monopolist s and social planner s cost minimizing durability choice in both the short and the long run when learning effects are present the model indicates that the relationship between durability and learning depends crucially upon whether or not knowledge decays and on learning s impact on the marginal cost of durability in particular this model demonstrates that swan s 1970 1971 independence result will hold in the long run if knowledge does not decay but will not hold if knowledge does decay thus whether or not monopolists will manufacture products with the same durability or quality as a social planner depends to a large extent on the type of learning process in the industry and on whether or not quality and durability directly influence this learning process

wright meets markowitz how standard portfolio theory changes when assets are technologies following experience curves abstract we consider how to optimally allocate investments in a portfolio of competing technologies using the standard mean variance framework of portfolio theory we assume that technologies follow the empirically observed relationship known as wright s law also called a learning curve or experience curve which postulates that costs drop as cumulative production increases this introduces a positive feedback between cost and investment that complicates the portfolio problem leading to multiple local optima and causing a trade off between concentrating investments in one project to spur rapid progress vs diversifying over many projects to hedge against failure we study the two technology case and characterize the optimal diversification in terms of progress rates variability initial costs initial experience risk aversion discount rate and total demand the efficient frontier framework is used to visualize technology portfolios and show how feedback results in nonlinear distortions of the feasible set for the two period case in which learning and uncertainty interact with discounting we compare different scenarios and find that the discount rate plays a critical role

information customization and food choice in this article we employ a hypothetical discrete choice experiment dce to examine how much consumers are willing to pay to use technology to customize their food shopping we conjecture that customized information provision can aid in the composition of a healthier shop our results reveal that consumers are prepared to pay relatively more for individual specific information as opposed to generic nutritional information that is typically provided on food labels in arriving at these results we have examined various model specifications including those that make use of ex post de briefing questions on attribute non attendance and attribute ranking information and those that consider the time taken to complete the survey our main results are robust to the various model specifications we examine

the learning curve in a competitive industry we consider the learning curve in an industry with free entry and exit and price taking firms a unique equilibrium exists if the fixed cost is positive although equilibrium profits are zero mature firms earn rents on their learning and if costs are convex no firm can profitably enter after the date the industry begins under some cost and demand conditions however firms may have to exit the market despite their experience gained earlier furthermore identical firms facing the same prices may produce different quantities the market outcome is always socially efficient even if it dictates that firms exit after learning finally actual and optimal industry concentration does not always increase in the intensity of learning

valuation of environmental and societal trade offs of renewable energy sources abstract use of renewable energy sources is one solution to decrease green house gas emissions and the use of polluting fossil fuels renewables differ in their environmental and societal impacts and to design sound renewable energy policy societies need to assess the trade offs between alternative sources to enable the evaluation and comparison of renewable energy production alternatives in finland this paper applies the choice experiment to elicit the monetary information on people s preferences for four renewable energy sources wind power hydro power and energy from crops and wood and considers four impacts of energy production effects on biodiversity local jobs carbon emissions and household s electricity bill the nested logit analysis reveals that higher income male gender young age and pro environmental attitude increase the probability to choose renewable energy instead of the current energy mix wind power is on average the most popular renewable energy technology but regional differences exist biodiversity deterioration should be avoided the national aggregate willingness to pay based on stated preferences rather than preferences revealed by actual market behavior for a combination of renewable energy technologies that corresponds to finland s climate change and energy policy is over 500 million euros

a learning curve model with knowledge depreciation abstract empirical studies in several industries have verified that unit costs decline as organizations gain experience or knowledge in production which is referred to as the learning curve effect in the past two decades there has also been analytical work on the relationship between a firm s learning curve effects and its pricing and output decisions learning rates differ significantly across firms in the same industry and recent empirical evidence has shown that knowledge depreciation may be an important reason for these differences we propose and analyze a learning curve model with knowledge depreciation and provide several new insights first we show that there exists a steady state where knowledge level and unit cost remain constant over time and there exists an optimal path to this steady state many empirical researchers have observed this plateau phenomenon whereby unit costs decline but reach saturation after some time while this has been traditionally modeled exogenously in the learning curve literature by assuming that cost reduction stops at some level of knowledge through a convex decreasing unit cost function we provide an alternative endogenous explanation we are also able to show that unlike in the model without knowledge depreciation the production rate along the optimal path to the steady state may decrease over time also the knowledge level along the optimal path may actually decline over time finally we show that the optimal production rate decreases at higher interest rates and increases at higher knowledge depreciation rates in turn this implies that a high interest rate environment discourages firms from achieving high knowledge levels and results in higher prices on the other hand higher knowledge depreciation rates result in higher production rates and lower prices

evaluating environmental investments a real options approach the paper presents a model that determines when at which output price level it is optimum for a firm to invest in environmental technologies and which are the main parameters that affect this decision our analysis shows that firms require high output price levels to be induced to invest in environmental technologies because they optimally would not want to commit to a heavy irreversible investment that could turn out to be unprofitable in the event of a price fall a comparative static analysis predicts that firms in industries with high output price volatility would be more reluctant to invest in environmental protection technologies and would be more willing to operate at low output levels thus attaining low emission levels increases in the interest rate would also reduce optimal environmental investment levels

the stochastic learning curve optimal production in the presence of learning curve uncertainty theoretical analyses incorporating production learning are typically deterministic costs are posited to decrease in a known deterministic fashion as cumulative production increases this paper introduces a stochastic 1earning curve model that incorporates random variation in the decreasing cost function we first consider a discrete time infinite horizon dynamic programming formulation of monopolistic production planning when costs follow a learning curve this basic formulation is then extended to allow for random variation in the learning process we also explore properties of the resulting optimal policies for example in some of the stochastic models we analyze optimal production is shown to exceed myopic production echoing a key result from the deterministic learning curve literature in other of the stochastic models however this result does not hold underscoring the need for extended analysis in the stochastic setting we also provide new insights in the deterministic setting for example

option pricing when the underlying asset earns a below equilibrium rate of return a note in their classic paper black and scholes 2 present two derivations of the european call option pricing formula the first which we will refer to as the replication derivation relies on the fact that the returns from the option can be replicated by holding a continuously revised position in the underlying asset and bonds this implies that if an option is not priced according to the blackscholes formula there is a sure profit to be made by some combination of either short or long sales of the option and underlying asset this argument is seemingly independent of considerations relating to capital market equilibrium the second derivation which we will call the equilibrium derivation evolves from the requirement that the option earn an expected rate of return commensurate with the risk involved in holding the option as an asset this note considers the pricing of a call option on an asset which earns an expected rate of return lower than that necessary to induce investors to hold it we show in this case that even if the replication strategy is feasible it is inefficient a consequence of this is that the correct option pricing formula is different than the black scholes formula unlike the black scholes formula our formula requires as an input the difference between the expected rate of return on the underlying asset and that expected rate of return which would be required to induce holding of the asset other papers have made a similar point constantinides 3 and cox et al 4 have argued that in equilibrium the prices of traded contingent claims must satisfy a partial differential equation which is identical to the black scholes partial differential equation only when the underlying asset pays no dividends and earns a rate of return sufficient to induce holding of the asset more recently ingersoll 5 has noted that commodities often pay a nonpecuniary service yield the value of which must be taken into account in deriving the option price none of these authors however explain why the black scholes formula is sometimes inappropriate the purpose of this note is to demonstrate why the black scholes formula needs modification even if replication is feasible we provide an intuitive derivation of the correct formula and discuss why divergences of the equilibrium price from the black scholes formula do not result in arbitrage opportunities

the learning curve and optimal production under uncertainty this article examines the implications of the learning curve in a world of uncertainty we consider a competitive firm whose costs decline with cumulative output because the price of the firm s output evolves stochastically future production and cumulative output are unknown and are contingent on future prices and costs we derive an optimal decision rule that maximizes the firm s market value produce when the price exceeds a critical level which is a declining function of cumulative output we show how the shadow value of cumulative production the total value of the firm and the decision to produce depend on the volatility of the price and other parameters uncertainty increases the critical price required for the firm to produce but also increases the value of thefirm thus during periods of high volatility firms facing a learning curve ought to be producing less but are worth more

the nature and significance of lionel robbins methodological individualism abstract lionel robbins definition of economics helped to buttress the centrality that individual choice acquired after the second world war this however was an unintended consequence of his seminal work underlying his definition of economics a novel approach to methodological individualism is advanced in which the isolated individual plays the role of a temporary device useful for analysing more complex social phenomena the paper outlines three types of methodological individualism and argues that robbins approach cannot be classified under any of them we thus propose a different category that of first step individualism robbins rationale for focusing on the isolated individual is not that social phenomena can be reduced to individual behaviour but rather that this is the best starting point for economics if it is to progress and be able to deal with more complex phenomena in the future

principles of stochastic dynamic optimization in resource management the continuous time case abstract a wide range of problems in economics agriculture and natural resource management have been analyzed using continuous time optimal control models where the state variables change over time in a stochastic manner using a firm level investment model and a model of environmental degradation this paper provides a concise introduction to continuous time stochastic control techniques the process used to derive the differential of a stochastic process is stressed and in turn is used to explain ito s lemma bellman s equation the hamilton jacobi equation the maximum principle and the expected dynamics of choice variables a basic extension of the dynamic duality literature is also provided where the hamilton jacobi equation is used to derive a stochastic and dynamic analogue of hotelling s lemma

market rivalry and learning by doing abstract the failure to link learning by doing to its market effects and the complementary failure to consider market models in which competition extends to the search for cost efficiency can have unfortunate implications for economic policy this paper considers how the firm s equilibrium investment in learning arises in a two period oligopoly implications of these results for the manufacture of high technology products particularly by japanese semiconductor firms are developed

does the volatility of commodity prices reflect macroeconomic uncertainty abstract while there exists numerous studies on the macroeconomic effects of oil and commodity shocks the literature is quite silent on the impact of macroeconomic uncertainty on oil and commodity prices and especially on their volatility this paper tackles this issue through the estimation of a structural threshold vector autoregressive tvar model on a sample of 19 commodity markets we aim at i assessing whether the effect of macroeconomic uncertainty shocks on commodity price returns depends on the degree of uncertainty and ii investigating the transfer from macroeconomic uncertainty to price uncertainty using a newly developed measure of commodity price uncertainty our findings show that both agricultural and industrial markets are highly sensitive to the variability and the level of macroeconomic uncertainty while the impact on precious metals is more parsimonious given their well identified safe haven role in time of economic turmoil in addition we find evidence that the recent 2007 09 recession has generated an unprecedented episode of high uncertainty in numerous commodity prices interestingly our analysis further reveals that volatility and uncertainty in prices can be disconnected this is especially true for the oil market as most important shocks in the 1990s and the beginning of the 2000s that lead to price volatility do not generate price uncertainty highlighting the relevance of our uncertainty measure in linking uncertainty to predictability rather than to volatility

a compound option model of production and intermediate inventories this article extends the option approach to valuing real assets by modeling the firm as a two stage process with bounded output rates in which the output of the first stage may be held as work in process in this setting the real asset becomes a compound option which if exercised gives the option to finish the work in process and sell the output as its final payoff the existence of intermediate inventories may arise as an optimal investment strategy for exploiting possible future price increases the framework allows us to analyze the effect of uncertainty on output rates and the effect of interest rates changes on inventory levels copyright 1993 by university of chicago press

technological platforms and diversification as the invention of fundamental new sciences spawns subsequent research discovery and commercialization core technologies branch into new applications and markets some of them evolve over time into many derived technologies whereas others are essentially dead ends the pattern of evolution and branching is called a technological trajectory an intriguing question is whether some firms can ride the trajectory by developing proprietary experience in a platform technology because the knowledge is proprietary firms that originate in industrial fields based on a platform technology acquire the technological skills to diversify and to mimic the branching of the underlying technological trajectory the ability to compete in hypercompetitive markets depends on the acquisition of know how that is applicable to a wide set of market opportunities such capabilities serve as platforms into quickly evolving markets to respond rapidly to market changes a firm must have already acquired fundamental compet

the learning curve and pricing in the chemical processing industries data on 37 chemical products are used to test a number of hypotheses about the learning curve and industrial price behavior the results document a strong and consistent learning effect learning is found to be a function of cumulated industry output and cumulated investment rather than calendar time standard economies of scale appear significant but small in magnitude relative to the learning effect variations in the slope of the learning curve are linked to differences in r d expenditures and capital intensity market concentration is found to be a strong influence on price flexibility and the timing of learningrelated price changes

the convoluted influence of robbins s thinking on the emergence of economics imperialism this article analyses the influence of robbins s thought on the subsequent development of economics imperialism first the analysis of some passages that have been overlooked up to the present in which the author explicitly expresses his disbelief in the omnipotence of the economic method makes it possible to argue that robbins did not share the confidence exhibited by the advocates of economics imperialism in the capacity of economics to explain non economic phenomena second this article shows that robbins describes the influence of real scarcity on human behaviour in terms of a static constrained maximization problem thereby confusing issues of method and scope in his writings this confusion facilitated the view that economics is a method without a proper subject matter and its later expansion into other fields in conclusion although robbins cannot be counted as an earlier promoter of economics imperialism the misunderstandings implicit in his writings paved the way for the emergence of this intellectual movement

investments of uncertain cost abstract this paper examines irreversible investment decisions when projects take time to complete and are subject to two types of cost uncertainty the first is technical uncertainty i e uncertainty over the physical difficulty of completing a project which is only resolved as the investment proceeds the second is input cost uncertainty i e uncertainty over the prices of construction inputs or over government regulations affecting construction costs which is external to the firm these two types of uncertainty have very different effects on the investment decision a simple investment rule is derived that maximizes firm value and is used to analyze the decision to start or continue building a nuclear power plant during the 1980s

real options and product life cycles in this paper i develop an option valuation framework that explicitly incorporates a product life cycle i then use the framework to value the real option to change a project s capacity standard techniques for valuing real options typically ignore product life cycle models and specify instead a constant expected growth rate for demand or price i show that this specification can lead to significant error in the valuation of capacity options in particular the standard technique tends to undervalue the option to contract capacity and overvalue the option to expand capacity this result has important implications for capital investment decisions especially in high technology industries that feature regular introductions of newly improved products

time to build option value and investment decisions abstract investment decisions and outlays are often made sequentially for example the rate at which construction proceeds is usually flexible and can be adjusted with the arrival of new information traditional discounted cash flow methods which treat the pattern of investment as fixed ignore this flexibility and understate the value of the project this paper uses contingent claims analysis to derive optimal decision rules and to value such investments we determine the effects of time to build opportunity cost and uncertainty on the investment decision for reasonable parameter values we show how a simple npv rule can lead to gross errors

investment and financing decisions with learning curve technology abstract the learning curve has a significant impact on production cost hence corporate profit in a number of industries while the learning curve is well recognized in the economics literature and its effect on operating costs and production decisions widely studied its effect on corporate investment has been largely unexplored to our knowledge there is one paper that examines this issue but it is limited to unlevered firms we therefore examine a levered firm s optimal investment and financing choices when using learning curve technology the main findings are as follows the effect of leverage on the investment decision depends on the level of debt using the optimal debt level will result in earlier and larger investment thus leverage has a positive effect on investment overall and the difference between levered and unlevered firm is an increasing function of learning speed the optimal leverage ratio without a borrowing constraint is an increasing function of learning speed with a borrowing constraint the investment decision is similar to the unconstrained borrowing case but the leverage ratio is initially increasing and subsequently decreasing in learning speed moreover it is a decreasing function over a wider range for a more stringent borrowing constraint for decreasing returns to scale technology and for a less volatile product market

monopolist pricing with dynamic demand and production cost this paper deals with pricing of a new product over time by a monopolist who maximizes the discounted profit stream the interdependency of cost and demand on cumulative production makes the problem inherently dynamic cost is assumed to be declining with cumulative production learning curve effect while demand is a function of price and cumulative sales representing word of mouth and saturation effects the paper addresses this problem in a general framework that includes several previous results as special cases and provides new insights in other situations while the learning curve and word of mouth effect cause prices to be lower than the price that maximizes immediate revenues the saturation factor has the opposite effect the price path over time is affected by these factors and the interest rate we characterize the price path under several different situations and interpret the results for policy guidelines