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Journal Articles

Fashions, habits and changing preferences: a simulation of psychological factors affecting market dynamics

Janssen, M.A. and W. Jager

2001 Journal of Economic Psychology 22(6): 745-772.


Markets can show different types of dynamics, from quiet markets dominated by one or few products, to markets with constant penetration of new and reintroduced products. This paper explores the dynamics of markets from a psychological perspective using a multi-agent simulation model. The behavioural rules of the artificial consumers, the consumats, are based on a conceptual meta-theory from psychology. The artificial consumers have to choose each period between similar products. Products remain in the market as long as they maintain a minimum level of market share, else they will be replaced by a new product. Assuming a population of consumats with different preferences, and social networks, the model simulates adoption of new products for alternative assumptions on behavioural rules. Furthermore, the consequences of changing preferences and the size of social networks are explored. Results show that the behavioural rules that dominate the artificial consumer’s decision making determine the resulting market dynamics, such as fashions, lock-in and unstable renewal. Results also show the importance of psychological variables like social networks, preferences and the need for identity to explain the dynamics of markets.

Keywords: Social networks; Changing preferences; Consumer behaviour; Lock-in


Changing industrial metabolism: methods for analysis

Janssen, M.A., J.C.J.M. van den Bergh, P.J.H. van Beukering and R. Hoekstra

2001 Population and Environment  23(2): 139-156.


Research in the field of “industrial metabolism” traditionally has been focused on measuring and describing physical flows of economic systems. The “metabolism” of economic systems, however, changes over time, and measuring material flows is insufficient to understand this process. Understanding the relation between economic activities and material flows can help to unravel the socio-economic causes of these physical flows. Three issues are addressed: The importance of spatial scales and trade flows, empirical analysis of relations between economic development and material flows, and treatment of behaviour of and interactions between stakeholders. For each of these issues, methods for analysis are suggested.

Keywords: industrial metabolismmaterial flowsstructural decomposition


Trade and recycling of used tyres in Western and Eastern Europe

van Beukering, P.J.M. and M.A. Janssen

2001 Resources, Conservation and Recycling 33(4): 235-265.


Truck tyres can cause significant environmental pressure through the life cycle. The main aim of this paper is investigate to what extent international policy measures on foreign trade, international recycling and harmonisation of legislation can contribute in effectively reducing environmental pressure caused in the truck tyre life cycle. A two-region simulation model, representing Western and Eastern Europe, is developed that integrates the complete life cycle, incorporates environmental impacts in its economic analysis, is technically dynamic by accounting for learning-by-doing effects, and allows for variations in trade of new and old truck tyres. In this study the economic, environmental and social effectiveness of harmonisation and trade measures in the European life cycle for truck tyre is tested. Several conclusions can be drawn from the model simulations. First, the environmental effects caused by the trade of used tyres from Western to Eastern Europe are of limited impact on the overall environmental damage caused by truck tyres. The consumption stage is by far the main contributor to environmental damage. Within the marginal analysis of trade, harmonisation of disposal fees illustrated to generate very limited positive results. The private and external costs in the solid waste management (SWM) stage are too limited to have a notable impact on the overall configuration of the European tyre life cycle. The introduction of strict laws on tread depth in Eastern Europe has a much stronger impact on material flows than the harmonisation scenario. This suggests that domestic policy measures should be the primarily focus on interventions in this stage of the life cycle, for instance, by improving the management of tyre pressure. Because trade of used tyres has little impact on the consumption stage, this issue should not get priority in European environmental programs.

Keywords: International trade; Recycling; Environmental policy; Tyres; Europe


Experimentation with household dynamics: the consumat approach

Jager, W., M.A. Janssen and C.A.J. Vlek

2001 International Journal of Sustainable Development 4(1): 90-100.


Despite the abundance of empirical data on household energy consumption, it is hard to predict future developments because of the complexity of the household system. Multi-agent simulation offers a tool to get a better understanding of the relevant behavioural dynamics of the household system. This would allow for an early diagnosis and response to unwanted developments. A computer simulation of consumer behaviour has been developed on the basis of a meta-model of behaviour, which integrates various relevant behavioural theories. This so-called consumat approach has been applied to issues such as the lock-in of consumption patterns and the management of a common resource, and has been applied in an integrated ecological-economic model. This paper discusses the basic principles of the consumat approach, summarises some results, and draws conclusions with respect to the application of this approach in the domain of household consumption.

Keywords: behavioural dynamics; consumat; consumer behaviour; household consumption; modelling; multi-agent simulation.


An immune system perspective on ecosystem management

Janssen, M.A.

2001 Conservation Ecology 5(1): 13.


A new perspective for studying the complex interactions between human activities and ecosystems is proposed. It is argued that biological immune systems share a number of similarities with ecological economic systems in terms of function. These similarities include the system’s ability to recognize harmful invasions, design measures to control and destroy these invasions, and remember successful response strategies. Studying both the similarities and the differences between immune systems and ecological economic systems can provide new insights on ecosystem management.

Keywords: adaptive systems, artificial immune systems, biological invasions, ecological economic systems, ecosystem management, immune systems, institutions, models.


An exploratory integrated model to assess management of lake eutrophication

Janssen, M.A.

2001 Ecological Modelling 140(1-2): 111-124..


Ecosystem management requires the explicit treatment of interactions between humans and ecosystems. An exploratory model for integrating social and ecological dynamics was introduced to study ecosystem management strategies. This paper focuses on the management of lake eutrophication. The model was developed to include the dynamics of the lake, the behaviour of agents using phosphorus for agricultural purposes, and the interactions between ecosystem and farmers. Analyses with the model showed that the dominating type of cognitive processing was a relevant factor in the response to uncertainty and policy measures. A higher target level for returns on the use of phosphorus was found to lead to a more intensive use of phosphorus and to higher levels of phosphorus in the lake. Simulated farmers used phosphorus more intensively in situations with high natural variability. A tax on phosphorus had little effect on the behaviour of the farmers when they felt uncertain and had low target levels for returns.

Keywords: Lake management; Social psychology; Resilience; Eutrophication; Multi-agent modelling; Integrated modeling.


Sequential optimization of integrated climate change models

Janssen, M.A.

2001 Mathematics and Computers in Simulation 54(6): 477-489.


A sequential optimization approach is applied to optimize the behavior of a complex dynamical system. It sequentially solves a large set of mathematical equations and next optimizes the behavior of a reduced-system, fixing certain variables of the larger original problem. These two steps are repeated till convergence occurs. The approach is applied to the problem of identifying response strategies for climate change caused by antropogenic emissions of different trace gases. The convergence properties are analyzed for this example.

Keywords: Sequential optimization; Sequential reduced-system programming; Dynamical system.


Homo Oeconomicus und Homo Psychologicus zwischen Fisch und Gold (in German)

Jager, W. and M.A. Janssen

2001 Oekologisches Wirtschaften 2: 14-17.


Die Lenkung der gegenwärtigen konsum- und produktionsmuster in eine nach- haltigere richtung erfordert eine ausführliche studie des menschlichen Verhal- tens. um dessen komplexität angemessen zu berücksichtigen, wird hier ein multi-agenten-ansatz vorgeschlagen, der erkenntnisse der sozialpsychologie integriert. am Beispiel des Übergangs von einer fischerei- zu einer Bergbauge- sellschaft wird gezeigt, wie sich unterschiedliche Verhaltensannahmen auf die mensch-umwelt-Beziehungen auswirken.


Book Chapters

Policy Case Studies: Netherlands – A life cycle analysis of tires in Western Europe

van Beukering, P.J.H. and M.A. Janssen

2001 In Environmental External Costs of Transport, edited by R. Friedrich and P. Bickel, pp. 274-277, Springer.

Computersimulatie als aanvullend gereedschap voor de sociaal psycholoog: De gedragsdynamiek achter overconsumptie uit een gezamenlijke bron verklaard met de consumat-benadering

Jager, W., M.A. Janssen and C.A.J. Vlek

2001 In Sociale Psychologie & haar toepassing, edited by J. Ybema, H. Aarts, W. Elving, M. Hagedoorn, pp. 169-180, Eburon Academic Publishers, Delft.


The Targets IMage Energy Regional (TIMER) Model, Technical Documentation

de Vries, H.J.M., D.P. van Vuuren, M.G.J. den Elzen and M.A. Janssen
2001 Report 461502024, National Institute for Public Health and the Environment, Bilthoven, the Netherlands.


The Targets IMage Energy Regional simulation model, TIMER, is described in detail. This model was developed and used in close connection with the Integrated Model to Assess the Global Environment (IMAGE) 2.2. The system-dynamics TIMER model simulates the global energy system at an intermediate level of aggregation. The model can be used on a stand-alone basis or integrated within the framework of the integrated assessment model IMAGE 2.2. The model simulates the world on the basis of 17 regions. The main objectives of TIMER are to analyze the long-term dynamics of energy conservation and the transition to non-fossil fuels within an integrated modeling framework and explore long-term trends for energy-related greenhouse gas emissions. Important components of the various submodels are price-driven fuel and technology substitution processes, cost decrease as a consequence of accumulated production (‘learning-by-doing’), resource depletion as a function of cumulated use (long-term supply cost curves), and price-driven fuel trade. The first chapter gives a brief overview of the model objective, set-up, and calibration method. In subsequent chapters, the various submodels are discussed, with the introduction of introduced concepts, equations, input assumptions, and calibration results. Chapter 3 deals with the Energy Demand submodel, Chapter 4 with the Electric Power Generation submodel, and Chapters 5 and 6 with the Fuel Supply submodels. Chapter 7 describes fuel trade and technology transfer modeling; Chapter 8, the Emissions submodel. In the last chapter, a few general concepts are discussed in some detail to improve the user’s understanding of the model. The TIMER-model has played a role in the following: the Special Report on Emission Scenarios (SRES) for the Intergovernmental Panel on Climate Change (IPCC), the European AirClim-project, the construction of global mitigation scenarios, and the Policy Options for CO2 Emission Mitigation in China project.


Co-evolution of cognitive strategies and the environment

Janssen. M.A., and Jager, W.
2001 paper presented at Simsoc 5 meeting on "Frontiers in Social Sciences Simulations" in Kazimierz Dolny (Poland), September 21-23.


In this paper, we focus on the cognitive costs that are involved in more reasoned decision-making strategies. We argue that a lower investment of cognitive effort may be beneficial both for the individual as for the sustainability of the population as a whole. We further argue that the most effective distribution of decision-strategies will be related to the stability of the environment people live in. Hence personality factors that determine the preference for a certain distribution are subject to evolutionary pressures. Experiments with a simulation model show that sustainability can be reached when cognitive costs are included in the model. Moreover, it is being demonstrated that evolutionary pressures favor a mix of cognitive strategies. Finally, we demonstrate that an unstable environment favors the development of a smaller population investing more cognitive effort in their decision-making process.


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