Jay Forrester quotes (work-in-process), various papers
- "Industrial Dynamics, a major breakthrough for decision makers", 1958
- "Common foundations underlying engineering and management", 1964
- "The structure underlying the management process", 1964
- "A new corporate design", 1966
- "Principles of systems", 1968
- "Industrial dynamics - after the first decade", 1968
- "Growth Cycles", 1977
- "System Dynamics and the lessons of 35 years", 1991
- "Policies,decisions and information sources for modeling", 1992
- Article: "The CEO as organization designer", 1992
- "System dynamics, systems thinking, and soft OR", 1994
- Article: "The beginning of system dynamics", 1995
- "Economic theory for the new millennium", 2003
- Article: "The prophet of unintended consequences", 2005
- "Some basic concepts in system dynamics", 2007
- "System Dynamics:the next fifty years", 2007
- Other J.W.Forrester Quotes
- Other Authors
"Industrial Dynamics, a major breakthrough for decision makers", 1958
"...I am interested in the development of a professional approach to management..."
"...too often management education consists of gathering current industrial practice and presenting it to the student as a series of unrelated subjects [...] and in his [subsequent] work in industry, his learning experience perpetuates the atmosphere of unrelated compartmentalization..."
"...these new management concepts will rest partly in [...] data processing, military research [resulting in] improved understanding of decision making and complex system simulation, [...] and on information feedback systems..."
"...in systems development for the military, it has been amply demonstrated that carefully selected formal rules can lead to tactical decisions that excel those made by human judgement under pressure of time and with insufficient experience or practice..."
"...from the military we have [...] methods of simulation for determining the behavior of complex systems [that] do not require undue mathematical ability..."
"...without an awareness of basic information flow principles, it is only through costly errors that managers can develop an effective intuitive judgement..."
"...Feedback theory explains how decisions, delays, and predictions can produce either good control or dramatically unstable operation..."
Policies,decisions and information sources for modeling
"...to begin [...] we need to know three kinds of information about the system: its organizational structure, the delays in decisions and actions, and the governing policies..."
"...the company will come to be recognized not as a collection of separate functions but as a system in which the flows of information, materials, manpower, capital equipment, and money set up forces that determine the basic tendencies toward growth, fluctuation, and decline..."
"...I want to emphasize the idea of [flow] not just [as] the simple three-dimensional relationships of functions [...] but the constant ebb and flow of change in these functions — their relationships as dynamic activities..."
"...the industrial dynamics program at MIT is aimed at four goals: [...] develop better intuition for time varying behavior, [...] show relationships between different aspects of a system,[...] help predict the future course of an organization, [and] improve the future prospects of a company..."
"Common foundations underlying engineering and management", 1964
"...the manager sees the technical man as narrow and lacking interest in people and social systems, even though the engineering is designing [a system] which may help the future manager better understand the complexity of social systems..."
"..the paramount problems in engineering have their origins in the management system [and] a preponderance of [...] managers are not equipped to solve these problems..."
"...management, economics, and much of engineering share [a] common foundation in feedback system behavior and psychology..."
"...having lived [...] in an era of the scientific frontier [it] may be difficult to recognize an era displacement. [...] The next decades may well transition focus [from] attention to science, [...] to understanding the dynamic behavior of our social systems..."
"...we might consider management of the future as 'enterprise engineering', [by] designing a system, principles of feedback control, a clear distinction between policy making and decision making, [and] the substitution of analytic solutions [by] simulation..."
"...social systems are customarily started without a clear statement of underlying philosophy and long-term goals [thus] no framework exists against which to measure shorter-term actions..."
"...companies and countries are usually evolved through trial-and-error [...] attention has been on individual problems [thus] the approach has been piecemeal instead of comprehensive..."
"...[in companies] conditions of the moment are evaluated by essentially static methods, and they govern actions without adequate investigation of the future (dynamic) implications..."
"...feedback control implies not only [...] error correction, but also the entire range of dynamic phenomena that occur within self contained systems..."
"...a system is described by its structure, transfer function,[and] time delays. Noise spectrum, bandwidth, natural frequencies, filter distortion, gain, and transient response must be considered..."
"...policy should be sharply distinguished from decisions. [...] Policies are those rules by which [...] information streams are converted into decisions to control activity. [in contrast] Decisions are continuously generated as a result of applying the Policy to the input data flows..."
"...management [will] distinguish [between] the decision maker and the policy designer [...] the former part of the active operation, [the latter] part of a higher level of abstraction..."
"...even when intuitive thinking attempts to cope with dynamic interactions, it goes little beyond visualizing single loop relationships. However, it is from multi-loop interactions that many difficulties arise..."
"...If the engineer is to succeed in contributing his special qualifications to the management area, he must be able and willing to extend and reinterpret his engineering philosophy and attitudes beyond the limits of pure technology..."
"...[by using industrial dynamics] engineers will bring to actual human organizations the courage to experiment with promising new approaches based on a foundation of design..."
"...a feedback system exists wherever the surrounding circumstances provide the inputs to a decision process which controls an action that is intended to alter the surrounding circumstances..."
"...[for example] the cobweb analysis [in economics] of commodity supply and prices reflects awareness of [...] closed loop interactions..."
"...if awareness of the existence of feedback systems is so widespread, one might ask if the feedback processes are well understood. The answer is negative. Every existing treatment of the subject penetrates a little more than the outer layer of what will become an increasingly important body of knowledge..."
"...feedback systems of greater complexity do not merely bring quantitative extension of behavior modes seen in simpler systems. Entirely new phenomena take place..."
"...our first step [in exploring Industrial Dynamics] was to develop a substructure which would give a skeleton for the main feedback structure of systems..."
"...simulation is the only possible route to handling complex non-linear systems. Mathematical analysis can deal only with the simplest of linear systems and [...] these systems do not exhibit the modes of behavior with which the manager must cope..."
"...the substructure [of Industrial Dynamics] is powerful and simple. It consists of two classes of variables [...] levels and rates..."
- "...level variables are accumulations within the system [...] indicate the order of the system [...] and describe the present state of the system..."
- "...rates represent activity [...] establish how the levels are changing [and] are the policies or decision-functions that cause the system to evolve..."
"...many of the problems in teaching [...] management arise because the subject is taught in isolation [since] inputs to a functional area come form other parts of the system [and] major consequences of local action may appear elsewhere..."
"...there can be no answer to the question of what information is needed unless one can trace the consequences of the existence or absence of specific information channels [...] only then can one see the consequences of distortion, delay, bias,error, and cross-talk in the information..."
"...the so-called intangibles [such as] psychological variables, integrity, reputation, financial pressure, speculative motivations and fear [...] must be included in our theory of system behavior. [...] There is no reason, except lack of courage on the part of the investigator, for omitting these concepts from our system representation..."
"...complex systems can behave differently under circumstances that superficially appear identical. Managers attribute to outside causes the system-induced crises that come from their own policies..."
"...we have found that graduate school is too late to begin with [the System Dynamics] approach to management..."
"A new corporate design", 1966
"..authoritarian and bureaucratic control structures mold individual personality [...] environment is seen as capricious, lacking in orderly structure and in cause-and-effect relationships. [...] the individual feels little hope of changing that environment, and is not open to information and observations that would lead to improvement..."
"...another form of discipline and control [...] arises from the self-interest created by the competitive market mechanism...
"... four measures of policy are important: [...] Freedom [this is] the extent to which they determine decisions, Accessibility [this is] the extent to which these policies are known to the decision maker, Source [this is] the policy position between two extremes [...] being completely self-determined [or] being completely imposed, and Consistency [this is] their freedom from internal contradiction..."
"...policy should allow for freedom to innovate [and] have the fewest restrictions needed to ensure system strength, stabilty and growth..."
"...policy-making should be separated from the distractions of operational decision-making [or] it will be postponed in response to short-term pressures..."
"...part of the policy design task is to identify the relative importance of the various decision points and to determine the quality and fidelity needed in each information input..."
"...much of the character and atmosphere of an organisation can be deduced from the way it externally extends and withholds information [...] in healthy organisations authority tends to rest on generally recognised superior ability, not excessively bolstered by information monopolies..."
"...information is often withheld forestall questions about an authoritarian decision that has no rational defence..."
"Principles of Systems", 1968
"... social systems [...] became so complex and their behavior [...] confusing, that no general theory seemed possible [and] a search for orderly structure , for cause and effect relationships, and for a theory to explain system behavior gave way at times to a belief in random, irrational causes..."
"...mere description has not been sufficient to expose the true nature of systems [and] mathematics has not been adequate for handling the essential realities of our [...] social systems..."
"...without an organizing structure, knowledge is a mere collection of observations, practices, and conflicting incidents [...] it is difficult to learn from experience, [and]] it is difficult to use the past to educate for the future..."
"...a systems strucrture should give to education in human affairs the same impetus that the structure of physicallaws has given to technology..."
"[regarding the endogenous point view]...where is the boundary, that encompasses the smallest number of components, within which the dynamic behavior under study is generated?..."
"...a discrepancy between the true system level and the information level that governs decisions always exists in principle..."
"Industrial dynamics - after the first decade", 1968
"...In physical systems the order is often defined in terms of the number of energy storage elements. In a system expressed as a differential equation the order is equal to the highest derivative. In a system expressed as a series of integrations the order is equal to the number of integrations. In a system expressed in first-order difference equations (which are integrations), the order is equal to the number of difference equations [...] In more practical terms, the order of the system is equal to the number of accumulations..."
"...positive feedback in the engineering literature is almost entirely omitted because the emphasis has been on steady-state control for maintaining equilibrium conditions..."
"...a system is nonlinear if it contains a multiplication or division of variables or if it has a coefficient which is a function of a variable..."
"...throughout our social systems, nonlinearity dominates behavior..."
"...to represent adequately managerial systems one must incorporate from two to twenty major loops, each of which may contain many minor loops..."
"...As one moves toward systems of greater complexity in any one of the [...] dimensions—order, inclusion of positive feedback, nonlinearity, and multiple loops—he finds that system behavior changes in major qualitative ways. The more complex systems do not merely show extensions of behavior seen in the simpler systems..."
"...Nonlinearity can introduce unexpected behavior in a system. A nonlinear system can be unstable for small disturbances but stable with sustained oscillation for larger disturbances [...] cause a feedback loop to shift its fundamental character between positive feedback and negative feedback [or] can cause dominance to shift from one loop in a system to another..."
"...[in] multiple loop system containing nonlinearities, the system behavior becomes surprisingly insensitive to change in values of a majority of the system parameters. In some system models, 90 % of the parameters can be changed individually by factors of as much as five without substantially affecting the system behavior..."
"...It may be helpful to distinguish two aspects of a system investigation—that relating to structure, and that relating to dynamic behavior [...] The two are intimately interwoven because it is the structure which produces the behavior..."
"...industrial dynamics is a philosophy of structure in systems [...] gradually becoming a body of principles that relate structure to behavior..."
"...Structure is seen as having four significant hierarchies:  The Closed Boundary,  The Feedback Loop as the Basic System Component [constituted by, 2] Levels (the integrations, or accumulations, or states of a system) [and] Rates (the policy statements, or activity variables, or flows") [and 4] Goals, Observed Conditions Discrepancy between Goal and Observed Conditions [and] Desired Action..."
"...A model of a system is formulated by starting with the loop structure, not by starting with components of loops..."
"...The rate variables are the policy statements of the system and within each there is explicitly or impicitly a statement of the goal of that decision-making point in the system, the observed condition, a discrepancy based on the relationship of goal and observed condition, and the desired action that results from the discrepancy..."
"...The feedback loop is fundamentally a closed process in which a decision, acting through time delay and distortion, influences the state of the system which, after further time delay and distortion, is detected as the observed state of the system..."
"...The boundary [in the industrial dynamics model] implies dynamic independence in the sense that any variable crossing the boundary from the outside is not itself a function of the activity within the boundary [...] anything not essential to producing the mode of behavior under study should be left outside the system boundary..."
"...[for] the skilled industrial dynamics analyst [...] establishing the system boundary comes first [followed by] the identification of feedback loops [to then] detai the level and rate substructure..."
"...We believe that the structure [of the industrial dynamic theory] will come to be recognized as having simple elegance, universality, and a fundamental character common to a very broad range of systems running from phj'sical devices through medicine and psychology to social and ecological systems..."
"...structure is a tremendous aid to organizing knowledge in a particular situation [and] one organizes knowledge for a purpose..."
"...an industrial dynamics structuring has almost no relationship to the normal corporate organization chart..."
"...Engineering systems are almost universally defined in terms of differential equations. But this seems artificial. It tends to focus attention on the wrong direction of causality. For example, if one is fillng a tank from a garden hose, our perception of reality suggests thinking of the water in the tank as the integral (accumulation) of the stream from the hose. The alternate statement, built around differentiation rather than integration, would define the water fiow rate from the hose in terms of the derivative of water level in the tank. This derivative formulation comes close to implying that the water fiows from the hose because of the change in water level. The differential equation formulation tends to obscure the direction of causality in systems..."
"...nowhere in nature does the process of differentiation take place [...] No instrument measures derivatives [...] devices which nominally measure rates of flow [...] measure average rates over some time span and operate on principles that involve integration [...] When a physical solution to a differential equation in engineering is to be obtained, as on a differential analyzer, the equation is first integrated enough times to eliminate derivatives [...] "Differential analyzer" is a misnomer; the machine is assembled from integrators..."
"...differentiation is seen as a mathematical artificiality which does not have a real life counterpart in the systems being represented..."
"...systems thinking and the ability to deal with dynamic interactions takes much longer to leam than the facts of the functional areas..."
"...there is a human tendency to resist change, so the evidence must often be more than abundantly clear before it induces a response...[however] no information is available to anyone that truly comes out of the future..."
"...in the economic system there are sometimes 'bootstrap' structures, when [the system] output depends on its own output. For example: if the beef industry wants to increase production output, it must first increase its breeding herds, and this is achieved by withholding stock from the market that would have been sold for meat. The result is an initial decrease in production output..."
"...the relationship between structure and randomness [states] that period and damping are determined by the structure of the system, and amplitude by the amount of noise..."
"...underlying minor randomness of everyday decision making are sufficient to feed in the signals that will keep an oscillatory system in a continuous state of motion [...] motion that will have a qualitative character determined much more by the structure and policies of the system, than by the nature of the noise..."
"...real life systems [...] smooth and filter noise to produce cyclic patterns. Any dynamic structure can be viewed as a filter..."
"...Entrainment is the process whereby a small amount of coupling in a system tends to draw together two or more cyclic modes that are of about the same period of oscillation [...] for example, it is reported that several pendulum clocks in the same room can begin to swing in unison because of the slight coupling through the structure of the room..."
"...there is an unwillingness to accept the idea that families, corporations, and governments belong to the same general class of dynamic structures as do chemical refineries and autopilots for aircraft..."
"...a new kind of management education [...] that we might call 'enterprise design' [and] the output of such an education is the role of 'enterprise designer'"
"...organizations built by committee, by intuition, and by historical happenstance often work no better than would an airplane built by the same methods..."
"... just as successful aircraft is possible only through skilled designers, so in future will competition create the necessity for enterprise designers who can reduce the number of design mistakes in the structures and policies of corporations..."
"...success will follow when the designs of corporations give greater emphasis to removing the causes of problems rather than trying to counteract the symptoms..."
"...Understanding of the dynamics of complicated information-feedback systems is so inadequate that that intuitive judgement should not be trusted to reveal even whether improvement or degradation will result from a given direction of policy change..."
"...[System Dynamics] uses to best advantage the extensive body of operating experience in people's heads wherein lies most of the available information about system structure and policies..."
"...[System Dynamics] realizes that a formal quantitative statement of policy carries no implication regarding absolute accuracy. We can make a formal quantitative statement corresponding to any statement that can be made in descriptive English. Lack of accuracy does not prevent quantifying ideas about policies. Assigning a number does not alter the accuracy of the original statement, but it does create a much more explicit basis for communication. The common belief that one cannot quantify decision rules because of lack of accuracy is confusing accuracy and precision. One can precisely make an inaccurate statement. We can quantify regardless of accuracy. After achieving precision of statement and communication, one can then deal with the question of what is sufficient accuracy..."
"...to omit a decision point is to deny its presence - a mistake of far greater magnitude than any errors in our estimate of the [decision] process..."
"...[System dynamics] must be alert to represent properly the 'worst-before-better' sequences that often arise. The short-term and long-term influences of a decision by a particular input, are often in opposite directions.."
"...System dynamics is a practical profession that starts from important problems, comes to understanding structures that produce undesirable symptoms, and moves on to finding changes in structure and policies that will make a system better behaved..."
"...often a person claims to understand system dynamics after using a particular modeling software. This is like saying that one is a qualified surgeon because of having used a knife [...] well developed and widely available tools often usurp center stage and divert attention away from the philosophy, insights, information sources, understanding of dynamics, and ability to conceive relevant model structures that together for the profession of System Dynamics..."
"The CEO as organization designer", 1992
when the fault lies in the situation into which they have been put [while] much of the time, it is the design of the organization that is defective..."
"...corporate design often allows, or even specifies, that decisions be made at the wrong places..."
"...for example, production managers should not decide production rates and sales managers should not set prices, because these decisions affect the corporate system far outside their own departments..."
"...management information systems tend to make more and more information available in more and more detail to more and more people until everyone is overwhelmed by excessive information focusing [the] scarce managerial attention on information streams that are not appropriate to the decisions being made..."
"...people usually react too quickly and do too much. They forget that often the right advice is, "Don't just do something, stand there." [...] Only a dynamic systems analysis can accurately show the consequences of a proposed policy..."
"...system dynamics can't help people who have no problems. Such people have no motivation for changing the way their organization operates..."
"...[for system dynamics to help] people must believe that their problems are largely caused by themselves [and] they can change what is causing their problems, rather than blame their problems on others. [then they] become interested in the nature of systems..."
"...[for system dynamics to help] there must be a desire to understand what is happening and why, instead of a grasping for superficial quick fixes..."
"...in general, a good time for CEOs to play the corporate designer role is when  their companies are very successful. But when a company is successful, people are less likely to become uneasy about the future  ...when a founder-manager who has built a successful company realizes he is not sure why the company is successful, and is doubtful about others carrying on after his retirement [and 3] when a new company is being organized..."
"...A system dynamics model usually shows how management is creating the problems that a company is experiencing. Very often the policies adopted to solve a problem are actually causing it. Then, as matters get worse, pressures increase to apply the policies more strongly still..."
"...Usually, everything needed to build an effective policy-oriented system dynamics model is available. The information is in the tremendous database in people's heads. They know who uses
which information, which decisions are made at each point in the system, how they are made, and what has happened in the past..."
"...A CEO without system dynamics skills should create a model along with someone who understands both the modelling process and the kinds of feedback structures that can create the problems, [as] the average manager or someone out of an ordinary business school or consulting firm will simply not know which dynamic structures to look for in conversations with operating managers..."
"...advisors [do] not to dictate what goes into creating a model: the model must come from the cor-
porate participants and be done by them.."
"...There is no guaranteed way to develop a worthwhile [system dynamics] model [...] How do you know how to design a successful airplane? [...] Success in system dynamics comes from understanding some deep fundamentals about the structure and behavioral dynamics of feedback systems..."
"...almost all existing organizations have been created without [a system dynamics model], and most people are unhappy with the results..."
"...In mathematical terms, the task of building real-world organizations that work is much more complex than that of solving a tenth-order, nonlinear differential equation. No engineer or mathematician can "solve" such a system by intuition and debate [and] it is unreasonable to
expect managers to do so..."
"...[flight simulator] games tend to focus on decision making; system dynamics focuses on the design of policies that guide decisions..."
"...[when Jay Forrester is asked how does one know if a system dynamics model is right:] There is no proof that Einstein's theory is right. There is no proof that Ohm's low in electricity or Boyle's law in gases are right. There is only an experimental demonstration that such laws are
useful for specific, limited purposes. There is no way of proving that a model or law or theory representing the real world is right. The same is true of a system dynamics model. It is a model of
structure and behavior that purports to represent something in real life. There can he no proof that it is right. That is not a meaningful question. The relevant question is the degree of confidence one has in a model..."
"...The competition for a system dynamics model is not a comparison against perfection, but a comparison against other models that would he used [as]all decisions are made on th basis of models..."
"...the alternative to a system dynamics model is almost always an inferior mental model that is already in use..."
"...start the modelling process with the most serious problem facing the company [...] I have
found [...] that important challenges are no harder to attack than unimportant ones - and the payoff from success is much greater..."
"...people often do not distinguish causes from symptoms or symptoms from solutions..."
"...Modern system dynamics practice [must] keep managers involved at every step of the process [so] when a useful model emerges, managers know how it happened and are more willing to accept the relevance of the results..."
"... even when shared understanding exists [of how undesriable behaviors are generated], established traditions and practices often keep a corrective policy from being adopted..."
"...education for implementation and getting acceptance of the required policies may be a greater challenge than the design [of a system dynamics model]"
"[from a systemdynamcs analysis] the corrective action called for reversing policies that three generations of top management had made public speeches about as the basis for their success. All three generations of former management were alive, in town, on the board, and stockholders. Logic has great difficulty prevailing in that kind of setting..."
"...business leaders make impassioned speeches about the advantages of a free enterprise economic system while running some of the largest socialist bureaucracies in the world. They have central planning, central ownership of capital, central allocation of resources, subjective evaluation of people, lack of internal competition, and decisions made at the top in response to internal political pressures. These are the fundamental characteristics of a socialist economy. The speeches by corporate executives are right; their practices are not..."
"...In all dynamic systems, similar modes of behavior lock together with even very slight coupling between systems. The technical term is 'entrainment'..."
"...System dynamics deals with concepts that have been almost entirely absent in [traditional] education, even though those concepts underlie everything that happens..."
"...the systems viewpoint is a paradigm, a frame of reference, a way of looking at one's surroundings, that takes a long time to internalize [...] Developing such a systems perspective takes less time with a young, inquisitive, and open mind than with one that has already been conditioned to see the world in terms of unidirectional cause and effect..."
"...System dynamics should not be taught as a separate subject but as a common thread running through all subjects..."
"...[when teaching system dynamics in schools] it appears that the prior academic ranking of students does not correlate with how well they do in a school organized around system dynamics and learner-directed learning..."
"...Some of the students who have traditionally ranked at the top are there because they can repeat information from lectures and books. But they may not truly understand its significance and so may do less well in dealing with dynamic relationships. On the other hand, some of the students who ranked at the bottom in conventional terms because they see school as irrelevant, may have keen insight into how the world around them is working, and are inspired by the way system dynamics allows them to build on the mental models they have already acquired..."
"System dynamics, systems thinking and soft OR", 1994
"...[difficulties] in moving from problem to solution [include] little guidance [...] for converting a real-life situation into a simulation model, [and] many system dynamics projects have fallen short of their potential because of failure to gain the understanding and support necessary for implementation..."
"...in the system dynamics process [...] understanding comes first, but the goal is improvement..."
"...unlike methodologies that focus only on an ideal future condition for a system, system dynamics should reveal the way we arrived at the present and then, in a later step, the path that leads to improvement..."
"...[model] adequacy does not mean proof of validity. There is no way to prove validity of a theory that purports to represent behavior in the real world. One can achieve only a degree of confidence in a model that is a compromise between adequacy and the time and cost of further improvement..."
"...the proper basis of comparison lies between the simulation model and the model that would otherwise be used. That competitive model is almost always the mental model in the heads of the people operating in the real system..."
"...I expect that system dynamics will continue to rest on experience, art, and skill for imagining the most creative and powerful alternatives..."
"...[model] implementation often involves reversing deeply embedded policies and strongly held emotional beliefs. It is not that people disagree with the goals, but rather how to achieve them [...] Even with widespread intellectual agreement with a system dynamics model and with the recommended improved policies, there may still be great discomfort with the prospect of changing from traditional actions..."
"...to overcome both active and passive resistance [to models] requires sufficient duration and intensity of education and debate to reverse traditional practices..."
"...The conceptualization phase of system dynamics has much in common with the soft methodologies, but system dynamics is disciplined by an organizing framework that leads to model formulation and simulation..."
"...Most misbehavior of corporate, social, and governmental systems arises from [a] dependence on erroneous intuitive solutions to complex behavior..."
"...Soft OR has evolved [...] as a reaction against the inability of classical or “hard” operations research to deal with the major issues of interest to managers and political leaders..."
"...I believe ineffectiveness of hard OR arose [by] the adoption of inappropriate mathematical methods [and because] hard OR became an academic discipline rather than a practical pro-
fession [as] hard OR drifted toward continued refinement of the very theories that kept it from engaging the real world..."
"...There is a [...] danger to system dynamics; academic research tends toward small technical
challenges rather than engaging the major concerns of the larger society..."
"...Systems thinking is coming to mean little more than thinking about systems, talking about systems, and acknowledging that systems are important. In other words, systems thinking implies a rather general and superficial awareness of systems..."
"...Causal loops do not provide the discipline to thinking imposed by level and rate diagrams in system dynamics. Lacking the identification of level variables, causal loops fail to identify the system elements that produce dynamic behavior..."
"...inventing a theory (model) comes most easily to the prepared mind that is operating within a relevant framework [...] a relevant structural framework disciplines thinking."
"...in system dynamics, a causally closed system is one in which the causes creating the behavior of interest lie within the system..."
Article: "The beginning of System Dynamics", 1995
"...we have not yet cracked the challenge of how to bring enough people across the barrier separating their usual simple, static view-point from a more comprehensive understanding of dynamic complexity..."
"...World Dynamics seemed to have everything necessary to guarantee no public notice: 40 pages of equations in the middle ofthe book; key messages in the form of computer output graphs; and a publisher that had only published one book before. I thought I was writing for maybe 200 people who would like to try an interesting model on their computers. But I was wrong..."
"...One often sees assertions in the social science literature that the act of studying an organization will alert people to questions about their actions, and that the process of being studied will cause changes in behavior. I do not believe this is true. It is much harder to change decision-making procedures [as] old mental models and decision habits are deeply ingrained; they do not change just because of a logical argument..."
"...to change the mental models that people use to represent the real world [...] individuals must
be sufficiently involved in the modeling process to internalize lessons about dynamic feedback behavior [and] start at an early age, before contrary patterns of thought have been irrevocably established..."
"...A case study, like a system dynamics analysis, starts by gathering and organizing information from an actual managerial setting. But the case study leaves this information in a descriptive form that cannot reliably cope with the dynamic complexity that is involved..."
"...System dynamics [...] can organize the descriptive information, retain the richness of the real processes, build on the experiential knowledge of managers, and reveal the dynamic behaviors that follow from different policy choices..."
"...corporate involvement with system dynamics goes much further than we can readily observe, because the best work is surrounded by a high degree of confidentiality..."
"...System dynamics deals with how things change through time. Almost all human concerns relate to how the past led to the present, and how today's actions determine the future..."
"Economic theory for the new millenium", 2003
"...as a result of trying to pose as a science, the field of economics has become substantially detached from real-world behavior, and has tended toward a closed theoretical discipline disconnected from the world it tries to explain..."
"...I suggest that economics should become a systems profession [...] parallel to management,
engineering, and medicine [...] based on underlying sciences such as psychology, decision-
making, and nonlinear feedback dynamics [...] to understand and redesign economic systems..."
"...I believe economics needs to return to theories based on observation of the real world, and
then test and improve those theories in simulation models..."
"...One often sees assertions about how fast economic change is occurring and how one could not create a model with constant policies that would be valid over 200 years. However, if one models from a sufficiently fundamental level, I believe that there is a structure that is almost unchanging..."
"...Most of the highly visible [economic] changes are superficial..."
"...Many years ago I was pressing a corporate president to try a radically different way for
organizing computers to process business information. In about the third meeting with him
and his chief programmer the president became interested enough to ask his programmer
how long it would take to try the idea. The technician’s answer was, ' My assistant and I
can do it in four months. If you give us another helper, we can finish in five months. With five
more staff it will take a year. With a team of ten, it will never be finished'... "
"...in a nonlinear model, the superposition theorem does not apply; the different modes do not exist separately, and do not simply superimpose on one another..."
"...there is no reason that a generic model should reproduce any specific historical time series. Instead, it should generate the kind of dynamic behavior that is observed in the systems that are being represented..."
"...I believe there is much too much attention given in economics, and in system dynamics,
to reproducing a specific historical time series. The dynamic character of past behavior is
very important, but the specific values at exact points in historical time are not..."
"...real monetary authorities are not exogenous to the economies within which they operate. They
respond to economic conditions, take actions, and respond to new economic situations that they may or may not have influenced..."
"...There is little connection between [microeconomics and macroeconomics]; microeconomics does not explain how the parts of the system interact to create the combined behavior. But one must believe that the interacting parts of the real system are producing its observed behavior. In the sys-
tem dynamics model that we are discussing, the microstructure creates the macrobehavior..."
"...I want to stress the importance in all modeling endeavors of starting from the generic or
common class of systems to which the special case belongs [...] Generic structures give a student powerful insights that are transferable from one setting to another..."
"...A generic model is a theory of how the class of member systems behaves. The theory arises from observation of the real system and from information that is almost always sufficiently available..."
"...To use only numerical data and to exclude information from the mental and written data bases means that one loses most of the available information about structure and governing policies..."
"...I believe that attempts to forecast future conditions is a losing game and has been a diversion that has carried economists away from far more productive work..."
"...the relationship, between the short time within which to make a reliable forecast and the long time required to affect the system, limits the usefulness of forecasting [...] As a result, and with only a little exaggeration, we can conclude that one can forecast in the time zone in which one cannot act, and can act in the time zone in which one cannot forecast..."
"...a system dynamics model should be used to forecast how the nature of the behavior of a system would be altered by consistently following an alternative policy..."
"...I believe that an underdeveloped area in system dynamics is the use of simulation models to critique descriptive theories about behavior [...] models derived directly from the described theories can be used to discover inconsistencies, omissions, and discrepancies between the theories and the
"...In mainstream academic economics there is little acknowledgment that the major depressions could be a dynamic mode that is separate from business cycles [this rejection] probably results from there being no systemic theory that could explain depression episodes that are decades apart..."
"...Most economists deny the existence of a systemic cause for depressions..."
"...A model is a theory that explains the behavior created by the model..."
"...Confidence in such a model depends on whether or not the structure of the model can be identified in the real world, how similar the model behavior is to the kind of behavior that has been observed, and how well changes in model policies result in changes in behavior that are reasonable and that have been observed in actual economies..."
"...[referring to the Kondratieff cycle] modeling has often revealed behavior that was unexpected, and for which there was no prior reference mode, but which was then found to exist in the real system..."
"...When such unexpected behavior occurs in a model, one should start by looking for errors in the model. However, as a model is improved, there is a rising chance that unexpected behavior is revealing something about the real system..."
"...it is much easier to bring system dynamics in at the grade-school level than it is at the graduate school , because there is much less to unlearn..."
"...people discover that their own policies inevitably generate their troubles [...] that is a very treacherous situation because if ylu believe that these policies solve the problem, and you do not see that they are causing the problem, you keep repeating more of the very policies that create the problem in the first place. This can produce a downward spiral towards failure..."
“I was never successful in getting the board to believe the models would work, [Forrester says]...The last time I tried, one of them said, ‘We agree that we’ve been successful following your advice, but it’s not because of your modeling. It’s just because you’re a better manager than we are.’ That excused them from having to pay attention to the source of my insights...”
“...We have not solved the challenge of how to bring enough people across the barrier separating their usual, simple, static viewpoint from a more comprehensive understanding of dynamic complexity...”
" [the Limits to Growth study] had everything necessary to guarantee no public notice, including 40 pages of equations..."
[Of his still-vocal critics regarding the Limits to Growth study, Professor Forrester says,] “...I don’t really expect to convert them. The only option is to outlive them...”
[When referring to Peter Senge's work] “...The trouble with systems thinking, is [that] it allows you to misjudge a system. You have this high-order, nonlinear, dynamic system in front of you as a diagram on the page. You presume you can understand its behavior by looking at it, and there’s simply nobody who can do that...”
“...People hate depressions because of the huge human problems they create, but they are also the windows of opportunity to new technology, and they’re the times when the stagnation and inefficiencies of the old corporate structure get liquidated [...] That clears the deck for a clean start and a more vibrant and efficient economy...”
"System Dynamics, the next fifty years", 2007
"...Why is there so little impact of system dynamics in the most important social questions? [...] the failure [...] lies directly with the system dynamics profession and not with those in government [...] Those in system dynamics are asking the wrong questions about the sources of low influence..."
"...One hears repeatedly the question of how we in system dynamics might reach “decision makers”. With respect to the important questions, there are no decision makers. Those at the top of a hierarchy only appear to have influence..."
"...big issues cannot be dealt with in the realm of small decisions..."
"...solutions to the most important sources of social discontent require reversing cherished
policies that are causing the trouble..."
"...before one can hope to influence government, one must build the public constituency to support policy reversals..."
"...We see many people trying to “dumb down” system dynamics into “systems thinking” and “causal loop diagrams”, which lack the power that is inherent in system dynamics. This may be because too many in the field lack the deep system dynamics competence necessary to convey and demonstrate the undiluted power of the field..."
"...Making system dynamics simple is a losing game. System dynamics is not simple. The problems of complex feedback systems are not simple. Reversing popular but harmful policies necessary to improve society is not simple. The simplified dilution of the field will fail and will discredit system dynamics so that even excellent work is suspect..."
"...those who take the road of systems thinking and causal loop diagrams are not practicing system dynamics. They remain dependent on the human mind for solving the dynamic behaviors..."
"...kind of forecast that system dynamics can reliably make [...] is the forecasting of the
kind of continuing effect that an enduring policy change might cause in the behavior of the system..."
"...exactly matching a historical time series is a weak indicator of model usefulness..."
"...Charactersitics of high quality system dynamics work:
1. Start with a clear description of the system shortcoming to be improved.
2. Display a compact model that shows how the difficulty is being caused.
3. Base description on a model that is completely endogenous with no external time series to drive it.
4. Argue for the model being generic and descriptive of other members of a class of systems to which the system at hand belongs.
5. Show how the model behavior fits other members of the class as policies followed by those other members are tested.
6. Arrive at recommended policies that the author is willing to defend.
7. Discusse how the recommended policies differ from past practice. "
"...we should not expect system dynamics to be easy to master. Designing an airplane is hard. Designing a bridge is hard. Doing a heart trans plant is hard. System dynamics is even harder..."
"...In a corporation, one can devote several years to moving the thinking of top executives to an understanding of dynamic behavior and the need for radical policy change. At about the time they are ready to act, they retire or die, and one must start over with a new group that must be conditioned from the beginning..."
"[to promote system dynamics] we need books from authors who are willing to be politically incorrect, who have the courage to attack sacred cows, and know how to show the public that
the emperors have no clothes..."
"... without a structure to interrelate facts and observations, it is difficult to learn from experience, this is, it is difficult to use the past to educate for the future..." - Jay Forrester
Forrester, J.W., 1968. Industrial dynamics—after the first decade. Management Science 14(7), pp.398-415.