If anything, the work on heuristics has shown that they can be fit for purpose, and are underpinned by their own rationality, i.e. My thoughts on this: Price is more or less an uncontrolled or exogenous variable so far as the individual farmer is concerned. This is particularly true in the realm of economic policy. Always nice to see discussion of techniques for managing uncertainty. Search on blog post titles and body text, category and tag text, and comments. Many profess Systems Thinking expertise, few have System Dynamics expertise. Previous question Next question Transcribed Image Text from this Question. Agree can be used in isolation or in combination. Travel hesitation. – ex. odds of being killed on a single airline flight are 1/29 million Estimated probability (uncertainty) – Most common, demands judgment Thanks for the reference (looks very relevant) and your thoughts, Joseph. An example of this is the uncertainty whether a second-hand Uncertainty about both decreases as experience is gained. This course deals with how uncertainty affects the actions and decisions of economic agents and how markets are impacted by the presence of uncertainty. Reference: He is a price taker and not a price maker. Risk, Uncertainty, and the Precautionary Principle 2. Walking Inflation. Especially when you add on top of that most peoples ignorance and understanding of lags, delays and dead times. Expected utility theory provides a useful approach to choice under uncertainty. Hedging is like insuring against an uncertain adverse outcome by offsetting potential losses associated with uncertain events by gains in other investments. In an uncertain environment, everything is in a state of flux. The farmer operates in a market structure which approximates to perfect competition and, therefore, the price he receives for a product of a given quality is altogether unaffected by any plan or courses of action that he or any other farmer might adopt. Uncertainty is a situation regarding a variable in which neither its probability distribution nor its mode of occurrence is known. I’ve had some experience exploring climate change scenarios (linked with historical environmental data) in workshops. We know that land is generally leased out to tenants. Complex systems such as an economy or events in the distance future involve greater uncertainty. This is particularly true in the realm of economic policy. Kahneman, D. and Tversky, A. reasoning. Another type of uncertainty that is quite conspicuous in agriculture is the tenurial uncertainty. What economics particularly brings to modelling is a basis in economic theory which is fundamental both to the building of the models and interpretation of the results along with focus on causal relationships and the explicit inclusion of uncertainty. Modeling helps reduce uncertainty by combining and structuring sources of information (including uncertainty about them). The concept acknowledges some fundamental degree of ignorance, a limit to knowledge, and an essential unpredictability of future events. The process is highly engaging and you get a good buy in from those involved in the process. A community blog providing research resources for understanding and acting on complex real-world problems. Scenario analysis is another method that can help to deal with uncertainty. This may be heresy coming from an economist who often builds models! The tenant, as farmer, does not know for how long he will be able to retain the land in his possession. A common strength of these approaches is that they explicitly consider uncertainty rather than ignoring it. TOS4. Enter your email address to follow this blog and receive notifications of new posts by email: We provide a list of terms (with definitions), which can be used to find all blog posts categorised or tagged with any particular term. Study the surprising outcomes from several government interventions in the U.S. economy. In response, economists have developed a large and active literature that attempts to measure uncertainty…Commonly used proxies of uncertainty…include: newspaper-based measures of uncertainty…finance-based measures…and measures of disagreement among forecasters for key economic variabl… Economic uncertainty in the UK can be illustrated by using these Bank of England forecast charts for economic growth. Biography: Emily Lancsar PhD is a Professor and Head of the Department of Health Services Research and Policy in the Research School of Population Health at The Australian National University in Canberra, Australia. Parameter uncertainty relates to the uncertainty around the ‘true’ costs and effects for each decision option because we are uncertain about the ‘true’ values of the inputs of the model. Economics has certainly been good at helping us make decisions: recognising trade-offs and making choices, if we agree on the payoffs, conditioned to risk and uncertainty. We find that, since 2008, economic policy uncertainty in the United States has been at a level approximately two times its long run average. Such models are used to reduce uncertainty regarding the question of value for money and guide government investment decisions. In additional to yield or technical uncertainty, uncertainty also exists with regard to the prices of agricultural products. A further complication is that different types of uncertainty will affect some sectors of the economy more than others. Response Uncertainty. Maier HR, Guillaume JHA, van Delden H, Riddell GA, Haasnoot M, Kwakkel JH (2016) An Uncertain Future, Deep Uncertainty, Scenarios, Robustness and Adaptation: How Do They Fit Together?. Welcome to EconomicsDiscussion.net! Product prices faced by the non-farm industries are also subject to fluctuations, but the degree of price uncertainty in these industries is much less than in agriculture. This happens because of the biological nature of agricultural industry which makes the yield much more dependent on natural factors in comparison with the products of non-farming industries. Most orthodox economists build models that are ‘static’ in the sense that statistical equations are fitted tightly to historical data. However, Government’s policy about land reforms and other institution may create some uncertainty which may be included under ‘Political uncertainty.’. Types of Probability a priori probability: known outcomes. The following points highlight the four main types of uncertainties experienced in agriculture. Where there’s this type of uncertainty, the big lesson is to keep options open and wait until you know the outcome. Although the terms are used in various ways among the general public, many specialists in decision theory, statistics and other quantitative fields have defined uncertainty, risk, and their measurement as: Modelling is used not only in economics, but also in a wide range of other disciplines and fields as attested by multiple contributions to this blog (see https://i2insights.org/tag/modelling/). Good for a historical perspective, but failing to address underlying dynamics. Her research has focused on economic evaluations, orphan drugs policy, health policy and patient reported outcomes. Thanks Kenny for your insightful comments, which overlap with Roman’s comment. The resources on our sister i2S website include tools, journals, professional associations and networks and conferences. Regression analysis is one but not the only analytical approach used in economics and we agree that accounting for underlying dynamics and momentum for change is important. Immediate events involving simple systems may be predicted very reliably. Fluctuations in crop yield take place over which the farmer has no control and which he is unable to foresee. This second kind of uncertainty, an uncertainty without delimiting parameters, has come to be known as "Knightian uncertainty," and is commonly distinguished in economics from quantifiable certainty, which, as Knight noted, is more accurately termed "risk." Most of the remedial measures that have been discussed below are concerned with the price uncertainty or the yield uncertainty as these two directly and immediately affect the earnings of the farmers and the farmers can also take some commonly accepted steps to meet these types of uncertainty. The problem is when we use such models to make predictions about future. Prospect theory: An analysis of decision under risk. Conditions may still be “sufficiently similar” even in cases where they have changed substantially, e.g. For instance, an oligopolist may be uncertain with respect to the market­ing strategies of his competitors. It’s therefore still useful for prediction whenever conditions are “sufficiently similar” to the original data. People’s uncertainty refers to the relationships of the farmer with persons he helps with. The types of exog- eenous shocks that can cause recessions—like wars, oil price jumps, and finous shocks that can cause recessions—like wars, oil price jumps, and fi nancial nancial This strong, or destructive, inflation is between 3-10% a year. In my sustainability teaching, my Master students were constrained to describing desirable (a normative activity) scenarios to inform policy. I’m curious in this case as to why these three were selected, and what others were perhaps considered before describing these ones? Ethical uncertainty arises if the agent cannot assign precise utilities to consequences. Given the subjectivity, that likelihood can differ from person to person. Even when events cannot be predicted exactly, only a modest level of decision uncertainty is present in such situations. We used rationality or lack of in a technical economics sense but fair point, especially given interdisciplinary audience, thanks for raising it. System dynamic models provide a great opportunity to do that, particularly for complex systems, and is one approach we are currently pursuing. State uncertainty refers to when a business manager is unable to determine what could happen as a result of the business environment. Gives more exact outputs than the basic search option. These differences in the relative degree of uncertainty apart, the important fact is that the individual farmer is unable to predict accurately the output that he will obtain from a particular input combination. These are Trice uncertainty, production uncertainty, Production technology uncertainty, Political uncertainty, Personal uncertainty and people’s uncertainty. •Construction is very sensitive to interest rates. System Dynamics is where Systems Thinking rubber hits the road. selection between alternatives based on expected utilities within a real options framework which involves investing in a portfolio of modelled short and long term actions, including insurance. The values that are chosen for the parameters of intertemporal social welfare functions are key inputs to IAMs, and are the subject of debate and, on occasion, controversy. It is harmful to the … Her broad research interests are in health economics, with a particular interest in understanding and modelling choice, preferences and behaviour of key decision makers in the health sector. Modern livestock husbandry is less dependent on weather in comparison to crop farming but a hard winter or a dry summer can still have a marked influence on livestock production. https://uonblogs.newcastle.edu.au/herdingthegreenchicken/, Sharing mental models is critical for interdisciplinary collaboration, Idea tree: A tool for brainstorming ideas in cross-disciplinary teams, Interdisciplinary competencies and innovation. uncertainty: “indefinite, indeterminate” and “not known beyond a doubt.” So in common usage, the distinction between the two is that risk denotes a positive probability of something bad happening, while uncertainty does not necessarily imply a value judgment or ranking of the possible outcomes. In the decision making environment of uncertainty, the information available to the manager is incomplete, insufficient and often unreliable. In particular, are there lessons from the discipline of economics which have broader applicability? Several external and random forces mean that the environment is most unpredictable. Moreover, the yield of some crops such as cotton is variable than that of others like wheat. – The primary weakness of static/empirical/regression model is that it is tied to the data used to develop it. … Biography: Siobhan Bourke PhD is a research fellow in the Department of Health Services Research and Policy, Research School of Population Health, The Australian National University in Canberra, Australia. It's … Before publishing your Articles on this site, please read the following pages: 1. Share Your Word File That’s fine if we are intent on predicting the past, and much of science is. Such an important issue to address. We would be interested in your experience in choosing which scenarios to model. •Mining operations are risky because metal prices have always been volatile. These kinds of models can be made to be ‘glass boxes’, interactive, and are superb learning tools – not intended to be crystal balls. Many other important managerial decisions are made under conditions of risk or uncertainty. Hedging takes an original decision problem and broadens the scope of alternatives to achieve “better” outcomes. Extensions and alternatives to expected utility theory have been developed to account for lack of rationality in human behaviour and cognitive biases. We extend our approach to other countries, finding elevated levels of economic policy uncertainty abroad, as well. 3 Sources of Uncertainty Inaccuracy in the estimates used in the study. Insurance markets are a typical example of institutions that have arisen to help economic agents deal with uncertainty. – Conversely, dynamic models are essential when conditions are known to have changed, where explanation of mechanisms is important, or where understanding of how a system changes is more important than simply predicting an end state. So, modelling and decision making, like driving, should be a dynamic process where we update and respond. because the model then provides a useful reference case, or simply a preliminary estimate for further work to improve upon. 2.3 Methodology of measuring economic policy uncertainty. The types are: 1. Expected utility theory is underpinned by an assumption of rationality. How can uncertainty be managed when all possible outcomes of an action or decision cannot be known? Hedging can be used to manage both risk and uncertainty. • Income estimates, • Operating expense estimates. In a world with shorter lead times, little or no buffer capacity, and quicker feedback loops, the traditional economics approach is no longer good enough. Excellent, thanks for the very practical examples. It can also involve a perceived zero probability in the case of unforeseen events (or ‘unknown unknowns’). That is a like driving while looking in the rear-view mirror! Attitudes regarding risk and uncertainty are important to the economic activity. I’ve three blog posts summarising different elements about scenario analysis that might be helpful for your readers too: see ‘Herding the Green Chicken’ https://uonblogs.newcastle.edu.au/herdingthegreenchicken/. We distinguish three qualitatively different types of uncertainty—ethical, option and state space uncertainty—that are distinct from state uncertainty, the empirical uncertainty that is typically measured by a probability function on states of the world. There are different forms of uncertainty. Static models also have a long history of being used to tackle “why” questions. Price Uncertainty: In additional to yield or technical uncertainty, uncertainty also exists with regard … That’s why the mess we are in and getting deeper. Uncertainty Uncertainty is a situation regarding a variable in which neither its probability distribution nor its mode of occurrence is known. A notable example is prospect theory (developed by Kahneman, a Nobel prize winner in economics, and Tversky, 1979) which describes how people choose between uncertain alternatives. ADVERTISEMENTS: The following points highlight the four main types of uncertainties experienced in agriculture. Sorry, your blog cannot share posts by email. Expected utilities provide a way of collapsing a probability distribution down to a point, to make it easier to choose between alternatives. This is certainly where other disciplines can draw upon economics, and many have. These persons include labourers (both family & hired), bankers, landowners., neighbouring farmers from whom the farmer leases in land or to whom the farmer leases out his land or other resources. Move over, the possibility of livestock epidemics is always there. In economics, Knightian uncertainty is a lack of any quantifiable knowledge about some possible occurrence, as opposed to the presence of quantifiable risk (e.g., that in statistical noise or a parameter's confidence interval). The EPU index was built by considering previous efforts and indices that attempted to measure economic uncertainty, and is based on three different aspects to measure uncertainty: newspaper coverage, stock market volatility, and expectations as gathered from business surveys. In particular, expected utility is the utility an individual (or some aggregate of people) is expected to obtain under different circumstances or ‘states of the world’. This course deals with how uncertainty affects the actions and decisions of economic agents and how markets are impacted by the presence of uncertainty. In times of real trouble, is a computer going to help you regain solid footing? These vary from the potential monetary rewards associated with entrepreneurial activity in business to the satisfactions of professional recognition and societal improvement for the innovative scientist. Yield uncertainty 2. Tenurial Uncertainty 4. ANSWER : GIVEN THAT : A few types of potential uncertainty in economic models of climate change view the full answer. The outside factors which affect prices are: (a) The behaviour of other farmers taken together; (b) weather-induced random fluctuations in output; (c) fluctuations in national income and prosperity; and. It is calculated by taking the weighted average of all possible outcomes with the weights reflecting the probability that a specific event will occur. A second type of socio-economic uncertainty is not really uncertainty at all, but rather disagreement about values. The underlying theory could best be driven by subject matter experts, modelling codified into mathematics recognising change, and economics can layer-onto these models its approach to valuation and making decisions. We highlight three approaches from economics that have broad value in managing uncertainty, especially for helping decision makers in taking uncertainty into account: expected utility theory, hedging, and modelling. Price Uncertainty 3. Understanding the ‘how’ as well as the ‘why’ increasingly important. Modelling―especially systemic representations of complex real-world scenarios and simulations that account for the subjective probability of such scenarios occurring―provides a way of assessing existing (and projecting future) inputs and outputs and systematically testing the impact of policies in ways that include and account for uncertainty. Political uncertainty refers to the uncertain political conditions in the country. Yield uncertainty 2. An alternative approach is dynamic modelling (e.g. Classification of Types of Uncertainty (Economic Language) The Economics of Climate Change –C 175 Risk: Unique probabilities describing the uncertainty Objective Subjective Ambiguity/Knightian uncertainty/deep uncertainty: Possible outcomes Uncertainty with regard to Input Prices/Quality. Future Events. Emily also leads the recently created ANU Health Policy Lab, premised on engagement and co-creation of research with policy makers and practitioners with the ultimate aim of contributing to improved health and wellbeing. The values that are chosen for the parameters of intertemporal social welfare functions are key inputs to IAMs, and are the subject of debate and, on occasion, controversy. Attitudes regarding risk and uncertainty are important to the economic activity. Share Your PPT File, Controversy regarding Farm Size and Productivity. How can researchers interested in complex societal and environmental problems best understand and deal with uncertainty, which is an inherent part of the world in which we live? Post was not sent - check your email addresses! The Bank of England believe the most likely forecast is in the centre (thickest black line) However, the range of the fan shows different possible outcomes. Price Uncertainty 3. However, the economics field in general can learn from other disciplines too. A second type of socio-economic uncertainty is not really uncertainty at all, but rather disagreement about values. Under normal circumstances, this type of uncertainty may not be there. Richard Bradley and Mareile Drechsler London School of Economics and Political Science July 12, 2013. Uncertainty due to the type of business and future health of the economy. One criticism – I prefer avoiding the idea of “lack of rationality in human behaviour”. Trouble with economics is that so much of it is based on regression analysis. Thanks for your thoughts, Joseph. Even though the term can be used in a technical sense, it is too easily misinterpreted as privileging a particular method of decision making over many others. We chose these techniques to demonstrate three different approaches. We need to understand and factor in the underlying dynamics and momentum of change, that’s why System Dynamics, not just Systems Thinking, is the only approach that addresses these. Thanks for this nice blog, and great to connect with others too. They keep us modest. I personally find inverse/bottom-up methods quite powerful – starting from outcomes and mapping back to what assumptions about the system and drivers can result in those outcomes. Treatment of Risk in Economic Analysis: Risk analysis involves a situation in which the probabilities … While uncertainty is often discussed alongside risk, a fundamental difference between uncertainty and risk is that risk involves events with known probabilities (or probabilities based on reliable empirical evidence), whereas under uncertainty probabilities are unknown and reflect an individual’s subjective belief concerning the likelihood of a given outcome. Within a dynamic approach scenario analysis can also become more realistic, and we can then appropriately use hedging and expected utility theory etc. The farmers generally react to this type of input price uncertainty by postponing the purchase of such inputs. “In this context, uncertainty refers to…lack of…clarity…about future economic activity…Uncertainty…is not directly observable. help quantify the role of risk and uncertainty in an economic analysis. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. The main reason for this is that not only are the non-farm industries much less affected by weather generated price fluctuations but also that the monopolistic market structure in which they operate enables them to exercise greater control over prices of their products. A forecast chart shows the range of possible forecasts for economic growth. This is certainly where other disciplines can draw upon economics, and many have. Uncertainty with regard to Input Prices/Quality. Our mission is to provide an online platform to help students to discuss anything and everything about Economics. But, at least let’s try and move beyond static models. Thanks Joseph for your thoughts. I was involved in one paper that tried to give an overview of different techniques, specifically focusing on the connection to uncertain futures and decision making under uncertainty: Best to keep our eyes wide open when driving, and our hands on the steering wheel. Abstract We distinguish three qualitatively di↵erent types of uncertainty - ethical, option and state space uncertainty - that are distinct from state uncertainty, the empirical uncertainty that is typically measured by a probability function on states of the world. Siobhan Bourke and Emily Lancsar are members of blog partner PopulationHealthXchange, which is in the Research School of Population Health at The Australian National University. Tourists looking to relax will often rule out destinations with any hint of instability. (1979). Future outcomes can be estimated with probabilities and predictions but typically remain unknown until they occur. The emphasis is upon the current effort to promote quantum probability as the most appropriate and reliable model for uncertainty in behavioral economics, both in human decision-making (e.g., in investment portfolio selection), and modeling of financial data, taking into account of human factor. Discussions can be very animated because a narrative is a powerful communication tool and a way of exploring assumptions that different people make. Disclaimer Copyright, Share Your Knowledge It highlights the importance of reference points and recognises that individuals may view potential losses differently from gains. 4). Agricultural Economics, Uncertainty, Uncertainty in Agriculture. Thanks for your thoughts, Roman. Risk and Uncertainty 1. doi:10.1016/j.envsoft.2016.03.014 The extent of yield fluctuation is, however, likely to be greater in some regions as compared to others. This type of uncertainty is particularly important in the case of capital inputs which are generally costly and subject to frequent qualitative improvements. Our modelling needs to get real. We highlight three approaches from economics that have broad value in managing uncertainty, especially for helping decision makers in taking uncertainty into account: expected utility theory, hedging, and modelling. Just one more dollop of 5 cents below, and slightly mischieveous . Personal uncertainty refers to the uncertainty about the welfare of farmer’s family. Thank you for the post. Like modeling itself, scenario analysis is a rather diverse field. Interested in your thoughts on the types of policy/research questions for which more static models may remain fit for purpose and when dynamic models are essential? Tenurial Uncertainty 4. As economists are fond of saying ‘there is no free lunch’; reducing the adverse outcomes of an uncertain outcome usually comes at a cost of a reduced rate of return in certain times for increased survival in adverse times. Have you applied economic approaches to uncertainty outside the discipline? Economics has certainly been good at helping us make decisions: recognising trade-offs and making choices, if we agree on the payoffs, conditioned to risk and uncertainty. Thanks Bonnie for noting scenario analysis as an approach to accounting for uncertainty which we agree, can be powerful, particularly when we have some a priori expectations about different scenarios that could arise. Many students found this difficult – maybe a naturally dystopian disposition. The relationship between the three is not clear, though they do seem to hint at a broader framework with gaps that have not yet been explored? All three could be used together, e.g. to inform government resource allocation decisions. There are different forms of uncertainty. „Uncertainty about both decreases as experience is gained. rolling a dice, roulette wheel Statistical probability: Observed frequencies used to predict outcomes. For instance, an oligopolist may be uncertain with respect to the market­ing strategies of his competitors. Once you know what effects a change in state will have for your business, you can then plan a response. Beware however, the mainstream won’t be happy! Share Your PDF File This uncertainty, which comes in three types, is one of the biggest issues facing small businesses. Price fluctuations are likely to be reduced further in case of industry because it is easier to adjust the supply of its products to changes in demand when compared with agriculture. A common strength of these approaches is that they explicitly consider uncertainty rather than ignoring it. For example, tropical regions are more prone to yield uncertainty than the temperate areas. Yield Uncertainty: In-spite of technical progress, crop yields is still very much dependent on natural factors and hence are […] Structural uncertainty is the most difficult type of uncertainty to define and to grasp. Generally speaking, the future is uncertain. List (but do not explain or elaborate on) three types of potential uncertainty in economic … Yet an other type of uncertainty is that which exists in regard to the price and quality of inputs. Yield uncertainty is also termed as technical uncertainty, as it refers to the variability in the production co­efficient of a given technique. Uncertainty as defined in this way is extremely common in economic activity. This can be achieved by taking a portfolio approach such that decision makers diversify across investments or courses of action. Insurance markets are a typical example of institutions that have arisen to help economic agents deal with uncertainty. A specific example is the development of decision analytic models to explore the cost effectiveness of health technologies (including drugs, devices, services, etc.) Uncertainty as defined in this way is extremely common in economic … – ex. We develop a new method to measure economic policy uncertainty and test its dynamic relationship with output, investment, and employment. We agree re the need for further use of dynamic models especially in complex interdisciplinary research. Actions taken in such a decision environment are purely speculative, such as … The types are: 1. This doesn’t prevent the negative (uncertain) event occurring, but reduces the adverse impact of that event, should it occur. November 17, 2020: Advanced Search option now available! Do you have other lessons from economics to share? Content Guidelines 2. Type # 1. Some economists, in order to be more comprehensive, have suggested six ‘Ps’ indicating uncertainties. In-spite of technical progress, crop yields is still very much dependent on natural factors and hence are highly uncertain. The types of exog-econd, why does uncertainty vary during business cycles? In economics, Knightian uncertainty is a lack of any quantifiable knowledge about some possible occurrence, as opposed to the presence of quantifiable risk (e.g., that in statistical noise or a parameter's confidence interval). „Uncertainty due to the type of business and future health of the economy. A further complication is that different types of uncertainty will affect some sectors of the economy more than others. He may thus hesitate to make long-term improvements in land as he may not be sure about earning the additional return from such improvements. The benefits are obvious in some types of risk taking. In a sense they are used for completely different purposes. Privacy Policy3. system dynamics, agent-based modelling) where the phenomena under study are represented in differential equations, and generating real-world complexity, such as interactions, feedbacks, tipping points, phase transitions. State Uncertainty. Decisions are made to maximise expected utility. Econometrica, 47: 263-291. Accidents happen, governments change, technological innovation occurs making some products and services obsolete, markets boom and inevitably go bust. Economic risk is the chance of loss because all possible outcomes and their probability of happening are unknown. For some types of uncertainty, no suggestion can be made to the farmer because nothing can be done at his own level e.g., Political uncertainty. But it did help to 1) work backwards to see what needed to be put into place to achieve that future and 2) applying a range of scenarios allowed them to determine if their proposed policy options were resilient to a range of futures. There was no practical way of stating the parameters of its occurrence—this kind of uncertainty is unquantifiable. Economics has been pretty hopeless in its modelled projections of future states of the world, from macroeconomics to climate models. It helps decision makers think about different options in terms of the probabilities of those options occurring and to rank them. 2] Uncertainty. Are there issues in dealing with uncertainty that economists could usefully apply themselves to? Some of these need further explanation. ECONOMICS OF UNCERTAINTY AND INFORMATION Giacomo Bonanno Department of Economics, University of California, Davis, CA 95616-8578, USA ... Another type of uncertainty concerns facts whose truth is already settled but unknown to us. https://www.thegreatcourses.com/courses/the-economics-of-uncertainty.html Types of Uncertainty. For others, like Personal uncertainty or people’s uncertainty, no suggestion of a general nature can be offered simply because the problem is too personal to be generalized. Government policies are a major source of uncertainty, since they can alter our lives in unpredictable ways. Build relationships. As economists increasingly move into health, environment, social policy etc, then an interdisciplinary approach may be best to help make better decisions. (d) discontinuous production cycles of the cobweb type. Environmental Modelling & Software 81 (July): 154–64.
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