In order to determine whether model testing is as useful as suggested by modeling experts, the full battery of model tests recommended by Forrester, Senge, Sterman, and others was applied retrospectively to a complex previously-published system dynamics model. The time required to carry out each type of test was captured, and the benefits that resulted from applying each test was determined subjectively. The resulting benefit to cost ratios are reported. These ratios suggest that rather than focusing primarily on sensitivity testing, modelers should consider other types of model tests such as extreme condition tests and family member tests. The study also finds that all of the different kinds of tests were either moderately useful or very useful--fully supporting the recommendations of the experts. An interesting diagram called a "tornado diagram" is used to portray the results of the sensitivity testing.
The tourism industry is considered a very important factor that contributes to the economic development Egypt. The industry has shown growth in the recent years in the number of tourist arrivals to reach a maximum of 6 million in 2003. It could not be denied that government efforts contributed to the growth but nevertheless the devaluation of the pound had a significant influence on the number of visitors. The performance of the industry might look fine in general. But, this is if compared to previous performance only. However, if an in-depth look is taken it is realized that the Egyptian tourism is performing far below capacity. This paper aims at explaining the way to improve the performance of the Egyptian tourism industry using a system dynamics methodology. This will be done by defining the main factors affecting the industry, then explaining how the whole system works and finally proposing a new modified model and required course of action.
The researchers attempt to visualize the complexity and dynamic behaviour of SME clusters in Egypt throughout the process of transferring a clusters state from static (idle) to dynamic (productive). This research constitutes the second of two complementary phases of a more comprehensive research that tries to quantify the qualitative measures of dynamic clusters through extending the application of the business dynamics tool to simulate the effect of different cluster-based economic development policy scenarios. After developing the mental model and during the conceptualization phase, the researchers highlighted the key-leverage causal loops showing feedback effects and uncovering the hidden cause effect relationships existing between the most important elements such as trust level inside the cluster, competition and the number of supporting industries. After validating the model, the researchers designed the policy analysis runs and undertook different scenario analysis over a time span of 50 years. Scenario analysis included studying the effect of elements such as institutions for collaboration (IFCs) on cooperation; effect of broker efficiency and success stories on trust building; and effect of trust on learning.
Dwindling government resources and demands for increased accountability have challenged nonprofit organizations to meet their primary missions while also creating efficient and effective back-office accounting and information systems. Even though many nonprofits say that accounting and information support systems are mission-critical, they tend to staff these systems weakly and to be less efficient than they could be. The present paper uses a system dynamics model to show how the Limits to Growth and Shifting the Burden systems archetypes help explain this situation. The model runs show that the exercise of leadership is the underlying issuenonprofit managers must challenge organizational cultures and mindsets that act as limiting factors, causing the nonprofits to avoid implementing fundamental solutions to their problems. The paper discusses several action recommendations.
This study reports of an experimental economics analysis of the new proposed Swedish-Norwegian tradable green certificate market (TGC). The green certificate market is a financial instrument to stimulate renewables within the context of liberalized, transnational electricity markets (a kind of market-oriented subsidy scheme). Green certificates are financial assets issued to green producers that can be traded freely. Previous system dynamics studies showed that trading- and investment behaviour were critical factors in analyzing the market dynamics. As a follow-up, this experimental economics study conducted 14 laboratory experiments with about 10 to 20 students per session. A particular feature is that participants handle both short-term trading and long-term investments, which allow us to analyze the interplay between these types of decisions without imposing behavioural assumptions on the model. The laboratory experiment shows that the market is likely to crash, due to the long time delays of supply side adjustment. The study provided new insights concerning agents trading and investment strategies, in particular the performance of various market designs. The mix of trading strategies employed in response to the experiments, are difficult to understand and capture in an SD model.
The paper describes a system dynamics model developed for dynamic analysis of human resource for the agricultural sector in different sources of employment, viz., government, private (including corporate), academic, financial institutes, non-governmental organizations, self employment, and others in India. Besides projecting an overall scenario for continuation of current agricultural education policy and trends, the paper analyses simulated results from the model for the current curriculum with 80:20 proportion of technical to soft skills. The analysis shows that in the coming years the private sector will emerge as a major employer for the graduates of agriculture and allied sciences.
Following several calls for participation in environmental policy, an increasing attention is being dedicated to the development of deliberative platforms for the sustainable governance of our global village. In this paper, we start by adding perspective on the role of participatory modeling within a strong participatory vision for sustainability. We then explore how system dynamics and ecological economics worldviews interlock in promoting participatory modeling approaches to environmental decision-making. Focusing on the synergies between group model-building and mediated modeling, some lessons from two participatory interventions developed in Portugal are extracted. The evaluation of the case studies indicates positive outcomes at the individual and group level, with respect to learning, reaction, commitment, communication and consensus. The outcomes at the organizational level are still more limited. Further research is suggested on the comparison and complementarity between participatory modeling and other deliberative methods.
The planning of investments for the ports of the North Atlantic range (Hamburg, Rotterdam, Antwerp, Le Havre, Goia Tauro) face a strong growth of the market (double over the next 10 years), large economies of scale, congestion in ports and hinterland connections, and strong competition for parts of the European hinterland. Several investment strategies can be followed. The present strategy has resulted in overcapacity. Modeling allows to trace the dynamic impacts from alternative strategies.
Health care in the Netherlands presents a unique mix of governmental and private responsibilities. Costs for long-term care, expensive treatments and uninsurable care for the complete Dutch population are covered by the Exceptional Medical Expenses Act (AWBZ), administered by 32 regional offices. Every health care provider operates under a contract with the regional administration office. Once contracted services are available, insurers are obliged to reimburse providers for these services even if they are not used by clients. In the coming years part of the Dutch health care will be deregulated and several types of care will be offered under market conditions. Whereas costs for care capacity are at present reimbursed by the government, this situation might change in the future. Regional care offices in general have little insight into long-term developments in supply and demand for health care. This paper describes a system dynamics study on demand and supply for a specific type of nursing care, dementia. The model shows how feedback between waiting lists and volume of different types of demand for care, leads to fluctuations in required capacity. The feared overshoot in long term nursing capacity did not materialize in model runs under a range of environmental scenarios.
Modelling the worldwide nuclear reactor park including all supply chain details, i.e. the nuclear fuel cycle, demands for an integrated nuclear energy system model which also includes feedback loops representing physical feedbacks within the system as well as, and most prominently, socio-political feedbacks in the decision-making on the various available deployment pathways for nuclear energy.
Argonne National Laboratory (ANL) started in 2000 with the development of such integrated nuclear energy system models, i.e. DYMOND and more recently DANESS. These models are based on system dynamics modelling used in various industry sectors and allowing to model the full mass-flow chain of time-varying mixes of nuclear reactor plants and associated fuel cycle options. Several other sub-models may then be coupled to the mass-flow kernel to calculate heat loads, economics, life cycle inventory, and several other parameters and feedback decision-making loops important in the assessment of nuclear energy futures.