System Dynamics Models: How to fly


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System Dynamics Models: How to fly

  1. 1. Small System Dynamics Models for Big Issues Triple Jump towards Real-World Dynamic Complexity Erik Pruyt | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |$| | | First time readers: start with the preface | |
  2. 2. Chapter 21 How to Fly 21.1 Pitfalls & Challenges for Novice SD Practitioners Following modeling mistakes are very common for novice SD practitioners: • Models are too big and/or too difficult/complicated: more time should have been spent conceptualizing and choosing a better level of aggregation. • The modeling process is not iterative enough: Start small and build out. From time to time, start all over again from scratch. Plan enough iterations – at least three serious ones. • Not enough time is budgeted: Be aware that modeling takes effort and time. Do not expect the first version of your model to be correct. Conceptualization takes time but could save even more time. Taking your time to build a good model saves a lot of time debugging and testing/rebuilding/testing/. . . and starting over again. • Too much time is spent on modeling and not enough time spent on using the model in a modeling process, e.g. for policy analysis and policy testing. Remember that, in the end, models are tools for thought. Policy-makers are interested in brilliant thoughts, not in detailed models and complex analyses. • Insufficient time and attention is paid to exploring alternative boundaries/formulations/. . . , exploring the consequences of alternative formulations, and reflect beyond the model(s). • Too much confidence/trust is attached to, and hard conclusions are drawn from, one among many plausible models. After all, multiple models can mostly be specified about the same issue. Models consist of many assumptions or micro-hypotheses that, together, constitute a macro-hypothesis about the system and plausible behavior. If the true underlying structure is not, or cannot be, known, then plausible models are all we can make. But given the fact that we could generate different dynamics and learn different lessons from different plausible models, it is often useful to develop and use different plausible models about the same issue. • Models are insufficiently tested and/or models are not really useful for the purpose at hand. Spend a lot of time testing your models. And ask System Dynamicists that are particularly good at model testing to test your models. Remember: all models are wrong, but some models are simply wronger than other models. Try to avoid the latter. Always try to make useful models: to do so, model in view of the purpose. • Models are often idealistic/unrealistic. Try to avoid making and using SD models with un- realistic assumptions or ‘without people in the model’. Add incentives, delays, traditions, 277
  3. 3. FLY: How to Fly c⃝ 2013 by Erik Pruyt typical (suboptimal) behaviors, and boundedly rational decision routines. Distinguish be- tween desired conditions and actual conditions, and between real conditions and perceived conditions. Decisions are made on the basis of perceived conditions, and can only be based on available information. This means that variables for which the value is not available (or measurable) in reality should not be used in decision making routines in the model. • Insufficient time spent on documenting the process and justifying the choices made in the modeling, analysis and policy design process. 21.2 From Here On. . . So far you only learned basic skills to build SD models and use them to perform basic analyses. I strongly advise anyone who got to this point to: • Read at least one of the following books: (Sterman 2000) and/or (Ford 2009). And those interested in more SD cases, are strongly advised to continue with Hartmut Bossel’s case books (Bossel 2007a; Bossel 2007b; Bossel 2007a). • Enrol in a SD project course under supervision of an experienced System Dynamicist. So far you acquired basic modeling skills, but not the necessary process skills, nor the experience it takes to apply SD for real. Then, take advanced SD courses. • Make models about any important dynamically complex issue you come across. • Attend SD conferences and gatherings, and especially the workshops at the end of the ISDC. • Start reading SD books, the System Dynamics Review, and other SD articles. See section 21.3 and 21.4 for a few suggested entries in the SD field and for each of the nine themes. 21.3 Introductory Reading & Additional SD Resources Highly recommended learning resources include (but are not limited to): • Excellent introductory SD books mixing explanations with exercises and cases, including recent ones such as (Ford 1999; Sterman 2000; Richmond 1992; Morecroft 2007; Warren 2002; Ford 2009; Meadows 2009), older ones such as (Forrester 1968; Richardson and Pugh 1981) and SD books in other languages (Aracil 1977; Boersma et al. 1995), as well as introductions to SD without exercises and cases such as (Randers 1980a). • The System Zoo books by Hartmut Bossel (Bossel 2007d; Bossel 2007a; Bossel 2007b; Bossel 2007c) which contain many SD models (follow this link to the zip file that contains all ZOO models), ranging from models with regard to physics and engineering (Bossel 2007a), over models with regard to climate, ecosystems, and resources (Bossel 2007b), to models with regard to economy, society, and development. Other SD exercises and case books, including (Goodman 1974; Mart´ın Garc´ıa 2006), and the series of Road Maps developed by the System Dynamics in Education Project (self-study guides bringing together important papers, books, and modeling exercises) and all the materials available through MIT’s open courseware. • K12 education materials at the Creative Learning Exchange, SD Games, and SD play book. • Study books introducing SD among other computational methods (Shiflet and Shiflet 2006) or to support domain studies such as studies in sustainable development (de Vries 2012). • Articles in journals such as the System Dynamics Review or Systems Research and Behavioral Science, as well as many articles in other scientific journals, articles in Proceedings of the International Conference of the System Dynamics Society, and notes, articles and theses in the MIT SD collection. | | | | | | | | | | | | | | | | | | | | | | |STOP | 278 | | | | | | | | | | | | | | |$| | |
  4. 4. c⃝ 2013 by Erik Pruyt FLY: How to Fly • Online simulators at Forio and at Insightmaker. • Other e-books including Money and Macroeconomic Dynamics by Kaoru Yamaguchi, a forth- coming interactive Systems Thinking book by Scott Fortmann-Roe and Gene Bellinger. • Excellent classic SD reads such as (Randers 1980a; Meadows et al. 1982; Meadows and Robinson 1985) and (Forrester 1961; Forrester 1969; Forrester 1971). 21.4 Further Reading per Theme There are also many excellent papers in the SD field, both in scientific journals and in the annual proceedings of the International Conference of the System Dynamics Society. A few books, papers, and special issues related to each of the nine themes are listed below. They are just the tip of the iceberg, hopefully providing enough of an entry into the SD literature related to each of these themes. | | Health Policy, Epidemiology & Drugs: (Homer 2012; Paich et al. 2009) (Thompson and Duintjer Tebbens 2007; Morrison et al. 2009; Homer et al. 2000) SDR special issue on Health and Health Care Dynamics. 15(3), 1999 | | Environmental & Ecosystems Management: (Forrester 1971; Fiddaman 1997; Ford 2009) (Moxnes 2000; Fiddaman 2002; Faust et al. 2004; BenDor and Metcalf 2006; Dudley 2008) SDR special issue on Environmental and Resource Systems. 20(2), 2004 SDR special issue on Sustainable Development. 14(2-3), 1998 SDR special issue on The Life of Dana Meadows. 18(2), 2002 | | Resource Dynamics & Energy Transitions: (Meadows et al. 1972; Bunn and Larsen 1997) (Ford 1990; Wils 1998; Dudley 2004) SDR special issue Environmental and Resource Systems. 20(2):89–198, 2004 SDR special issue on Sustainable Development. 14(2/3), 1998 SDR special issue on The Life of Dana Meadows. 18(2):101-310, 2002 | | Safety, Security & Risk: : (Wils et al. 1998; Cooke 2003; Cooke and Rohleder 2006; Anderson 2011) : SDR special issue on Terrorism, etc. (forthcoming) : Bibliography of the Special Interest Group on Conflict, Defense & Security | | Policing & Public Order: | | | | | | | | | | | | | | | | | | | | | | |STOP | 279 | | | | | | | | | | | | | | |$| | |
  5. 5. FLY: How to Fly c⃝ 2013 by Erik Pruyt (Weaver and Richardson 2006; Hovmand et al. 2009; Carter and Moizer 2011) | | Housing Policy & Urban Planning: (Forrester 1969) (Eskinasi et al. 2009; Alfeld 1995) SDR special issue on System Dynamics and Transportation. 26(3), 2010 | | Education & Innovation: (Milling 1996; Abdul-Hamid and Madnick 1991; Georgantzas and Katsamakas 2008) and (Andersen 1990) SDR special issue on Education 9(2), 1993 SDR special issue on Information Systems Research with SD. 24(3), 2008 |$| Economics & Finance: (Yamaguchi 2013) (Radzicki 1990; Saeed 1998) | | Management & Organization: (Forrester 1961; Sterman 2000; Warren 2002) (Gary et al. 2008; Weil 2007) SDR virtual issue on Project Management SDR special issue on the Dynamics of Supply Chains and Networks. 21(3), 2005 SDR special issue on ST and SD in Small-Medium Enterprises. 18(3), 2002 SDR special issue on Consulting and Practice. 17(3), 2001 | | | | | | | | | | | | | | | | | | | | | | |STOP | 280 | | | | | | | | | | | | | | |$| | |
  6. 6. Flexible E-Book for Blended Learning with Online Materials Although this e-book is first and foremost an electronic case book, it is much more than just a set of case descriptions: it is the backbone of an online blended-learning approach. It consists of 6 concise theory chapters, short theory videos, 6 chapters with about 90 modeling exercises and cases, many demo and feedback videos, feedback sheets for each case, 5 overall chapters with feedback, 5 chapters with multiple choice questions (with graphs or figures), hundreds of online multiple choice questions, links to on-site lectures, past exams, models, online simulators, 126 slots for new exercises and cases, and additional materials for lecturers (slides, exams, new cases). The fully hyperlinked e-version allows students (or anybody else for that matter) to learn –in a relatively short time– how to build SD models of dynamically complex issues, simulate and analyze them, and use them to design adaptive policies and test their robustness. ISBN paperback version: ISBN e-book version: