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John Morecroft

My life was changed by Jay Forrester. His influence came in two distinct ways; from personal encounters and from the research environment he created as founder and leader of the System Dynamics Group at MIT-Sloan. I spent a decade at MIT, first as a doctoral student and later as a member of faculty at Sloan. So there is much to remember. I will select a few personal stories to capture a sense of Jay as the special person and academic pioneer I came to know.

My stories are organised in three parts: early encounters, the academic environment, and contact in later years.

Early Encounters

In autumn 1975 I left England to join the doctoral program at MIT. I remember vividly arriving in Cambridge under New England’s crystal blue skies and searching out the headquarters of the System Dynamics Group in Building E40 across from the Sloan School. I was hoping to catch my first glimpse of Jay Forrester. I stepped into a colourful and spacious working area and, in a distant office, I spotted a gentleman with curly grey hair and the archetypal look of an absent-minded professor. I was surprised and a little disappointed. I’d been expecting someone more austere and intense; an image in my mind from a tiny black-and-white photograph of Jay that appears on the front cover of Industrial Dynamics. It was some days later I realised my mistake when the real Jay Forrester stepped into view with a lively and penetrating look on his face and upright stature that conveyed an instant sense of graceful authority and intellect. The absent-minded professor was someone else entirely. Such are the small-but-important first impressions and anxieties of new doctoral students.

Over the next few years Jay became a familiar presence in my life. I would not say he was a close acquaintance like a friend or contemporary. He was reserved, self-contained, clear thinking – yet welcoming. In the summer of 1977 he invited me to visit his family ranch in the Sandhills district of Nebraska. I was driving across the US with my wife Linda. We arrived at the ranch, ten square miles of rolling territory, to be greeted by Jay at the farm gate. He was wearing his cowboy hat, boots and riding gear. The contrast with his normal MIT attire (smart suit and tie) was astounding. Yet it made sense. He’d grown up among homestead pioneers and he went on to become an academic pioneer; an original thinker-and-doer, self-sufficient, fearless and rigorous. He and his wife Susan made us feel at home during our brief stay as they shared their homestead life. We strode around the grounds. Jay asked us to join him on horseback; but we were not skilled riders. He said he’d never learned to ride a bike. He told us of Nebraska storms so violent and intense that the brilliance of lightning was broken only by flashes of darkness.

Contact in Later Years

If I’ve created an impression that Jay can profoundly influence one’s life and thoughts from a distance – with penetrating intellectual force – then I’ve succeeded in communicating part of his remarkable ability. Clarity of thought and sense of purpose are rare gifts and it is a privilege to have learned in the presence of someone who possesses these gifts. Jay’s distinctive intellectual force permeates his seminal books Industrial Dynamics, Urban Dynamics and World Dynamics and can be observed throughout a pioneering life: from his Nebraska homestead upbringing; to the frontier of MIT’s engineering and computing research; and onward to the new frontier of System Dynamics in management. For more details I refer the reader to biographical articles by Fisher 2005 (The Prophet of Unintended Consequences) and Lane 2007 (The Power of the Bond Between Cause and Effect).

My contact with Jay in later years was sporadic though his influence did not diminish. A few stories remain vivid enough to reveal the person behind the sharp intellect. I remember a chance conversation at MIT on the covered footbridge that connects the old Sloan School Building E52 with the Dewey Library E53. By then I was a junior faculty member at Sloan. Jay began talking about his own career; something he’d never done with me before. He recalled the time when he was leading the Whirlwind computer project at MIT’s Lincoln Labs in the late 1950s. He had needed (and found) an alter-ego in a co-researcher called Bob Everett; someone whose technical brilliance was matched by a natural ability to reach out empathetically to other members of the project team. He wished he could find someone similar again. The conversation then turned to the challenge of communicating research. He said it was vital to reliably sense, and then to believe, one’s work could be important; important enough to make a difference in the world. It was a glimpse into the pioneer’s mind set. I knew instinctively he wished me and others to find, within ourselves, the same intellectual self-sufficiency and confidence. It was a perceptive yet gentle criticism.

Another story comes from a guest lecture Jay delivered in one of my classes. I used to run a semester-long course for MBAs and PhDs on “Applications of Industrial Dynamics”. The course required students to conceptualise and build a model addressing a practical business policy problem. I thought it was important to include a lecture on model conceptualisation (the task of deciding which factors to include in a model and which to leave out). So I invited Jay to talk about his experiences. He picked two quite different examples from his repertoire of vintage projects: the corporate growth model he built for the fledgling Digital Equipment Corporation in the early 1960s, and the World Dynamicsmodel from the early 1970s.

His lecture had a powerful effect on my students (and me too). He began by holding-up a single sheet of paper. It contained two large ovals – one labelled “company” and the other labelled “market”. Between these two ovals were lots of named connecting arrows, some going from the company to the market and some going the other way. He then went on to explain that this single page with its ovals and arrows was the result of two years model conceptualisation while he was sitting on the board of the newly formed Digital Equipment Company. He stressed that his efforts were by no means full-time. But more importantly he emphasized his need for all this elapsed time to think how best to approach the problem of representing Digital as a growth firm. Along the way he had rejected many possibilities to avoid detail unnecessary for exploring the dynamics of a firm’s growth over a ten-year period (for example he chose to ignore individual product lines, many of which would come and go over ten years). Thereafter only eight weeks were required to create the entire growth model of 200 equations.

After explaining much more about the structure of the Digital Equipment model he then moved to his second example – World Dynamics. At this point he displayed a two-page diagram from the World Dynamics book that shows the complete stock and flow structure of the World 2 model and the coordinating network of links. He then said he’d sketched a rough first-draft of this picture on a paper napkin in an eight hour transatlantic flight from Paris to Boston, following a meeting of the Club of Rome! The contrast between the two examples was dramatic. Two years for a sector map of Digital Equipment Corporation, and eight hours for a close-to-complete structural diagram of World Dynamics. The lecture showed, in a memorable way, the unusual combination of creativity, patience and disciplined thinking required for model conceptualisation.

I returned to the UK in the mid-1980s and joined London Business School where I have pursued my academic career ever since. Jay has remained a distant but ever-present influence. Most recently I met him at the 2013 conference of the System Dynamics Society in Cambridge MA. Aged 95 he still inspires an auditorium full of conference delegates. Even among friends he is apt to surprise. With an astute comment, he switched a dinner conversation of witty anecdotes to lively debate about the future of the field. After his talk on the closing evening of the conference there followed the screening of the 2013 documentary film ‘Last Call’ with its remarkable archive footage from the Club of Rome and the World Dynamics/Limits to Growth projects. It is a testament to Jay’s creative genius and foresight that a model conceptualised more than 40 years ago still engages people today as they grapple with unintended consequences of global industrial growth. Incidentally, the latest addition to my book collection is a first edition of World Dynamics, published in 1972 and signed by Jay Forrester in 2014.

Learning and Research Environment at MIT

There was a very special learning environment in the MIT System Dynamics Group at the time: hardworking, focussed, applied; yet rigorous and academic. Part of the environment was Building E40 itself – factory-like, practical, well-equipped, minimalist in décor; far from the dreaming spires of imagined academia. But more important was what went on inside Building E40. Doctoral students were dotted around an open-plan area at grey-metal desks surrounded by bookshelves and filing cabinets. Inside those filing cabinets was a remarkable collection of working papers; the so-called D-memo series containing thousands of documents about the group’s work. Graduate students were expected to contribute to the collection and it was perfectly normal for them to submit three or four major revisions of any manuscript in order to achieve acceptable clarity and quality.

Good modelling requires technical prowess, but the underpinning of mathematics and simulation should not displace clear reasoning and writing. Jay Forrester would scrutinise manuscripts of any researcher engaged in his projects. The documents would be returned covered in red comments and criticism. Another D-memo revision; another round of comments. The comments were often shared among graduate students. There were also Jay’s standard ‘tests’ for clear writing: can the document easily be read out-loud without stumbling over words and phrases; does the document make sense if only the first sentence of each paragraph is read? Another D-memo revision; another round of readability tests. You live with these criteria for years and you assume research is always conducted in this way. It is only later you realise just how special your training has been. The D-memo series (and accompanying criticism) embodied Jay’s research values with their emphasis on good writing, meticulous documentation and clear interpretation of models, equation formulations and simulations.

Jay’s values also emphasised applied research with real-world impact. Insights were to be gleaned from the everyday operations of business and society; backed-up by serious theory (in the form of models) and experiments (in the form of simulations). These personal values found unique expression in the group’s projects. I still remember the sense of excitement as a first-year doctoral student arriving by plane in Columbus, Indiana, headquarters of Cummins Engine Company. There I worked on the Cummins manufacturing dynamics project that Jay had originally started at the invitation of the company’s Chairman and CEO J. Irwin Miller. There was also a project with Harley-Davidson motorcycle company, plus the lingering aura of bold societal models and simulators from projects recently completed; including Urban DynamicsWorld Dynamics and the Limits to Growth. Jay forged an exciting, relevant research portfolio around business and societal issues: helping responsible people to unfold the futures of their firms, cities and industries; then devising new policies to make things better.

Jay became my PhD thesis supervisor. He was not one to spend hours per week coaxing a thesis out of a reluctant graduate student. Our contact was limited; yet it was inspiring and demanding. His view of supervision was pragmatic and dispassionate. He had created a research group, and had invested the effort to carve-out legitimate ‘intellectual space’ within MIT’s competitive academic hothouse. That was his job. Now it was now the responsibility of the young researcher to deliver good work.


Cerasuolo, E. (2013). Last Call. A documentary by Italian film director Enrico Cerasuolo about the history, impact and main protagonists of the Limits to Growth project (accessed 17 January 2014).

Fisher L 2005. The prophet of unintended consequences, strategy+business 40, Booz & Co.

Lane DC 2007. The Power of the Bond Between Cause and Effect: Jay Forrester and the Field of System Dynamics, System Dynamics Review, 23 (2/3), 95-118.

MIT System Dynamics Group 2003. D-memo Archive Working Paper Collection on DVD, available from the System Dynamics Society.