Acceptance of system dynamics models

[jforestr@MIT.EDU (Jay W. Forrest]

In his March 20 communication, Wolpert observes, " During
the past five years 25% of my time has been spent in Phase II:
trying to introduce the model and its implications. I am finding
terrific resistance in Phase II. My first hand awareness of this
resistance has made it clear that Phase II resistance is the
common lot of all system dynamicists who attempt to apply or
introduce their model. The most obvious case is the resistance
experienced by Prof. Forrester and his unsung heroic followers
associated with the World Dynamics Project."

My experience has been very different from that which Wolpert reports.
Perhaps two different situations should be identified.

First is when a system dynamicist works with a client to create
understanding and to solve a problem. The team works together and
acceptance is generated along the way. The challenge here is not to get
acceptance after a model has been created, but rather to establish the
initial working relationship that unites the system dynamicist with a
client that realizes a need for modeling. The client comes before the
modeling.

The second situation fits the setting described by Wolpert and also the
World Dynamics model. Here, the modeler decides that a projected model
will be accepted and found useful after the model is complete and
presented. The system dynamicist takes the risk of judging what will be
of interest to future potential recipients. Wolpert seems to be
describing a model that he feels is important but it appears that others
are not sharing his enthusiasm. That is very different from the World
Dynamics model to which he refers.

For those who may be unfamiliar with events following the publication of
World Dynamics, a little history may be of interest. The public
response was totally different from what I had expected. The book
seemed to have everything necessary to guarantee no public notice:

1. It has 34 pages of equations in the middle of the book.

2. The interesting results are in the form of graphs vs. time,
which many of the public cannot read easily.

3. The book deals with issues up to a hundred years in the future
and lie outside the presumed time of interest to the public.

4. The book was brought out by a publisher that had published only
one prior book, and I doubted that it had the commercial stature to be
reviewed.

5. The model in the book was the product of only two Saturdays of
work. The book took another four months to write, edit, and get all the
computer runs onto consistent scales. Even so, the total effort was
only a small fraction of that devoted to my other books.

I believed the World Dynamics book was for perhaps a hundred people who
would like to see how one can organize a mental model into an
interesting simulation exercise. That was the worst prediction I have
ever made.

The book came out the first week of June 1971. On the last week of June
it was reviewed on the front page of the London Observer, which at that
time circulated around the world. I received a letter from a faculty
member in one of the State Universities of New York asking for more
about what we were doing because he had been reading about it in the
Singapore Times. In August the Christian Science Monitor devoted all of
the first page of its second section to the book. In September it
received a page and a half in Fortune, in October a column in the Wall
Street Journal. World Dynamics was being debated in the editorial
columns of mid-America newspapers, and in the environmental,
zero-population growth, and underground anti-establishment student
presses. In the middle of the political spectrum, World Dynamics was
the subject of a full length article in Playboy. It was the subject of
prime time television documentaries in Europe.


The public response was a good hundred fold over what could have been
rationally expected. World Dynamics is still in print and available
from the Productivity Press in Portland, Oregon.

"The Limits to Growth" by Donella Meadows, et. al, Universe Books, came
out nine months later in March 1972. The message was essentially the
same as in World Dynamics. Much work had been done to verify
assumptions and to refine and extend the model. It was more popularly
written and did not have equations. Even so, it seemed that The Limits
to Growth might be an anti-climax after the vigorous public debate
about World Dynamics. Wrong again in the same way. Public discussion
went up by a factor of ten from where it had been. As one person in
Washington told me, "No one is entitled to have no opinion about Limits
to Growth." His estimate was, even though the book was initially
politically non-discussable in some government quarters, that some four
out of seven people agreed with it. A dinner meeting, attended by about
60 chief executives of major corporations and government agencies, was
held at the Century Club in New York to discuss The Limits to Growth.
Limits to Growth sold 400,000 copies in the first summer in the Dutch
language alone. It has been translated into probably 40 languages.
Beyond explanation, I received the Vietnamese translation of Limits to
Growth during the US-Vietnam war.

Gerald Barney had been associated with the Urban Dynamics, World
Dynamics, and Limits to Growth activities. Within the US Government, he
carried on the thread of activity to write the "Global 2000 Report to
the PResident: Entering the Twenty-First Century," (Penguin, 1982),
which was sent by President Carter to heads of states of all countries.
Barney is now director of the Millennium Institute in Arlington, VA,
email millennium@igc.apc.org, which is providing modeling of growth and
environmental issues for several countries.

Following the publication of World Dynamics and LImits to Growth, The
International Institute for Systems Analysis in Austria held annual
meetings on world modeling for ten years.

Richardson, John M., Jr., 1978. "Global Modelling: 2. Where to Now?"
Futures, Vol. 10, No. 6, pp. 476-491.

Forrester, Jay W., 1982. "Global Modelling Revisited." Futures, Vol. 14,
No. 2, pp. 95-110. From a lecture at the IIASA Global Modelling
Conference, Laxenburg, Austria, Sept. 1981.

Many universities held debates on growth following the two books. There
was considerable polarization of viewpoint. North American academic
economists were generally very negative. Strong support came from
students, the public, and corporate chief executive officers (in
contrast to middle level executives). The books sharpened the debate
about population growth and environmental issues.

Contrary to Wolperts comment, it seems that the followup to World
Dynamics was rather more than might reasonably be expected from two
Saturdays of modeling.

Jay W. Forrester
Germeshausen Professor Emeritus and Senior Lecturer
Room E60-389
Massachusetts Institute of Technology
Cambridge, MA 02139, USA
tel: 617-253-1571
email: jforestr@mit.edu

[jsterman@MIT.EDU (John Sterman)]

those interestes in the world modeling issues Jay raised in his last
message should also read

Dana Meadows, John Richardson, and Gerhart Bruckmann, 1982, Groping in
the dark: the first decade of global modelling. Chichester: John
Wiley.

It is a wonderful book with both hard technical detail on the many world
models and their strengths and weaknesses, and also personal discussion
about the conflicts, values, and ethical issues involved in modeling the
planet as a whole.

John Sterman
jsterman@MIT.EDU

[jsterman@MIT.EDU (John Sterman)]

those interestes in the world modeling issues Jay raised in his last
message should also read

Dana Meadows, John Richardson, and Gerhart Bruckmann, 1982, Groping in
the dark: the first decade of global modelling. Chichester: John
Wiley.

It is a wonderful book with both hard technical detail on the many world
models and their strengths and weaknesses, and also personal discussion
about the conflicts, values, and ethical issues involved in modeling the
planet as a whole.

John Sterman
jsterman@MIT.EDU