Club of Rome: The Limits to Growth (short version)


Richard Moore


The Limits to Growth

Abstract established by Eduard Pestel. A Report to The Club of
Rome (1972), by Donella H. Meadows, Dennis l. Meadows, Jorgen
Randers, William W. Behrens III

Short Version of the Limits to Growth

Our world model was built specifically to investigate five
major trends of global concern - accelerating
industrialization, rapid population growth, widespread
malnutrition, depletion of nonrenewable resources, and a
deteriorating environment.

The model we have constructed is, like every model, imperfect,
oversimplified, and unfinished.

In spite of the preliminary state of our work, we believe it
is important to publish the model and our findings now. (...)
We feel that the model described here is already sufficiently
developed to be of some use to decision-makers. Furthermore,
the basic behavior modes we have already observed in this
model appear to be so fundamental and general that we do not
expect our broad conclusions to be substantially altered by
further revisions.

Our conclusions are :

1. If the present growth trends in world population,
industrialization, pollution, food production, and resource
depletion continue unchanged, the limits to growth on this
planet will be reached sometime within the next one hundred
years. The most probable result will be a rather sudden and
uncontrollable decline in both population and industrial

2. It is possible to alter these growth trends and to
establish a condition of ecological and economic stability
that is sustainable far into the future. The state of global
equilibrium could be designed so that the basic material needs
of each person on earth are satisfied and each person has an
equal opportunity to realize his individual human potential.

If the world's people decide to strive for this second outcome
rather than the first, the sooner they begin working to attain
it, the greater will be their chances of success.

All five elements basic to the study reported
here--population, food production, and consumption of
nonrenewable natural resources--are increasing. The amount of
their increase each year follows a pattern that mathematicians
call exponential growth.

A quantity exhibits exponential growth when it increases by a
constant percentage of the whole in a constant time period.

Such exponential growth is a common process in biological,
financial, and many other systems of the world.

Exponential growth is a dynamic phenomenon, which means that
it involves elements that change over time. (...) When many
different quantities are growing simultaneously in a system,
however, and when all the quantities are interrelated in a
complicated way, analysis of the causes of growth and of the
future behavior of the system becomes very difficult indeed.

Over the course of the last 30 years there has evolved at the
Massachusetts Institute of Technology a new method for
understanding the dynamic behavior of complex systems. The
method is called System Dynamics. The basis of the method is
the recongnition that the structure of any system--the many
circular, interlocking, sometimes time-delayed relationships
among its components--is often just as important in
determining its behavior as the individual components
themselves. The world model described in this book is a System
Dynamics model

Extrapolation of present trends is a time-honored way of
looking into the future, especially the very near future, and
especially if the quantity being considered is not much
influenced by other trends that are occuring elsewhere in the
system. Of course, none of the five factors we are examining
here is independent. Each interacts constantly with all the
others. We have already mentioned some of these interactions.
Population cannot grow without food, food production is
increased by growth of capital, more capital requires more
resources, discarded resources become pollution, pollution
interferes with the growth of both population and food.

Furthermore, over long time periods each of these factors also
feeds back to influence itself.

In this first simple world model, we are interested only in
the broad behavior modes of the population-capital system. By
behavior modes we mean the tendencies of the variables in the
system (population or pollution, for example) to change as
time progresses.

A major purpose in constructing the world model has been to
determine which, if any, of these behavior modes will be most
characteristic of the world system as it reaches the limits to
growth. This process of determining behavior modes is
"prediction" only in the most limited sense of the word.

Because we are interested at this point only in broad behavior
modes, this first world model needs not be extremely detailed.
We thus consider only one general population, a population
that statistically reflects the average characteristics of the
global population. We include only one class of
pollutants--the long-lived, globally distributed family of
pollutants, such as lead, mercury, asbestos, and stable
pesticides and radioisotopes--whose dynamic behavior in the
ecosystem we are beginning to understand. We plot one
generalized resource that represents the combined reserves of
all nonrenewable resourCes, although we know that each
separate resource will follow the general dynamic pattern at
its own specific level and rate.

This high level of aggregation is necessary at this point to
keep the model understandable. At the same time it limits the
information we can expect to gain from the model.

Can anything be learned from such a highly aggregated model?
Can its output be considered meaningful? In terms of exact
predictions, the output is not meaningful.

On the other hand it is vitally important to gain some
understanding of the causes of growth in human society, the
limits to growth, and the behavior of our socio-economic
systems when the limits are reached.

All levels in the model (population, capital, pollution, etc.)
begin with 1900 values. From 1900 to 1970 the variables agree
generally with their historical value to the extent that we
know them. Population rises from 1.6 billion in 1900 to 3.5
billion in 1970. Although the birth rate declines gradually,
the death rate falls more quickly, especially after 1940, and
the rate of population growth increases. Industrial output,
food and services per capita increase exponentially. The
resource base in 1970 is still about 95 percent of its 1900
value, but it declines dramatically thereafter, as population
and industrial output continue to grow.

The behavior mode of the system is that of overshoot and
collapse. In this run the collapse occurs because of
nonrenewable resource depletion. The industrial capital stock
grows to a level that requires an enormous input of resources.
In the very process of that growth it depletes a large
fraction of the resource reserves available. As resource
prices rise and mines are depleted, more and more capital must
be used for obtaining resources, leaving less to be invested
for future growth. Finally investment cannot keep up with
depreciation, and the industrial base collapses, taking with
it the service and agricultural systems, which have become
dependent on industrial inputs (such as fertilizers,
pesticides, hospital laboratories, computers, and especially
energy for mechanization). For a short time the situation is
especially serious because population, with the delays
inherent in the age structure and the process of social
adjustment, keeps rising. Population finally decreases when
the death rate is driven upward by lack of food and health
services. The exact timing of these events is not meaningful,
given the great aggregation and many uncertainties in the
model. It is significant, however, that growth is stopped well
before the year 2100. We have tried in every doubtful case to
make the most optimistic estimate of unknown quantities, and
we have also ignored discontinuous events such as wars or
epidemics, which might act to bring an end to growth even
sooner than our model would indicate. In other words, the
model is biased to allow growth to continue longer than it
probably can continue in the real world. We can thus say with
some confidence that, under the assumption of no major change
in the present system, population and industrial growth will
certainly stop within th next century, at the latest.

To test the model assumption about available resources, we
doubled the resource reserves in 1900, keeping all other
assumptions identical to those in the standard run. Now
industrialization can reach a higher level since resources are
not so quickly depleted. The larger industrial plant releases
pollution at such a rate, however, that the environmental
pollution absorption mechanisms become saturated. Pollution
rises very rapidly, causing an immediate increase in the death
rate and a decline in food production. At the end of the run
resources are severely depleted in spite of the doubled amount
initially available.

Is the future of the world system bound to be growth and then
collapse into a dismal, depleted existence? Only if we make
the initial assumption that our present way of doing things
will not change. We have ample evidence of mankind's ingenuity
and social flexibility. There are, of course, many likely
changes in the system, some of which are already taking place.
The Green Revolution is raising agricultural yields in non
industrialized countries. Knowledge about modern methods of
birth control is spreading rapidly.

Although the history of human effort contains numerous
incidents of mankind's failure to live within physical limits,
it is success in overcoming limits that forms the cultural
tradition of many dominant people in today's world. Over the
past three hundred years, mankind has compiled an impressive
record of pushing back the apparent limits to population and
economic growth by a series of spectacular technological
advances. Since the recent history of a large part of human
society has been so continuously successful, it is quite
natural that many people expect technological breakthrough to
go on raising physical ceilings indefinitely.

Will new technologies alter the tendency of the world system
to grow and collapse?

Let us assume, however, that the technological optimists are
correct and that nuclear energy will solve the resource
problems of the world.

Let us also assume a reduction in pollution generation all
sources by a factor of four, starting in 1975.

Let us also assume that the normal yield per hectare of all
the world's land can be further increased by a factor of
two.Besides we assume perfect birth control, practiced
voluntarily, starting in 1975.

All this means we are utilizing a technological policy in
every sector of the world model to circumvent in some way the
various limits to growth. The model system is producing
nuclear power, recycling resources, and mining the most remote
reserves; withholding as many pollutants as possible; pushing
yields from the land to undreamed-of heights; and producing
only children who are actively wanted by their parents. The
result is still an end to growth before the year 2100.

Because of three siumultaneous crises. Overuse of land leads
to erosion, and food production drops. Resources are severly
depleted by a prosperous world population (but not as
prosperous as the present US population). Pollution rises,
drops, and then rises again dramatically, causing a further
decrease in food production and a sudden rise in the death
rate. The application of technological solutions alone has
prolonged the period of population and industrial growth, but
it has not removed the ultimate limits to that growth.

Given the many approximations and limitations of the world
model, there is no point in dwelling glumly on the series of
catastrophes it tends to generate. We shall emphasize just one
more time that none of these computer outputs is a prediction.
We would not expect the real world to behave like the world
model in any of the graphs we have shown, especially in the
collapse modes. The model contains dynamic statements about
only the physical aspects of man's activities. It assumes that
social variables--income distribution, attitudes about family
size, choices among goods, services, and food--will continue
to follow the same patterns they have followed throughout the
world in recent history. These patterns, and the human value
they represent, were all established in the growth phase of
our civilization. They would certainly be greatly revised as
population and income began to decrease. Since we find it
difficult to imagine what new forms of human societal behavior
might emerge and how quickly they would emerge under collapse
conditions, we have not attempted to model such social
changes. What validity our model has holds up only to the
point in each output graph at which growth comes to an end and
collapse begins.

The unspoken assumption behind all of the model runs we have
presented in this chapter is that population and capital
growth should be allowed to continue until they reach some
"natural" limit. This assumption also appears to be a basic
part of the human value system currently operational in the
real world. Given that first assumption, that population and
capital growth should not be deliberately limited but should
be left to "seek their own levels", we have not been able to
find a set of policies that avoids the collapse mode of

The hopes of the technological optimists center on the ability
of technology to remove or extend the limits to growth of
population and capital. We have shown that in the world model
the application of technology to apparent problems of resource
depletion or pollution or food shortage has no impact on the
essential problem, which is exponential growth in a finite and
complex system. Our attempts to use even the most optimistic
estimates of the benefits of technology in the model did not
prevent the ultimate decline of population and industry, and
in fact did not in any case postpone the collapse beyond the
year 2100.

Unfortunately the model does not indicate, at this stage, the
social side-effects of new technologies. These effects are
often the most important in terms of the influence of a
technology on people's lives.

Social side-effects must be anticipated and forestalled before
the large-scale introduction of a new technology.

While technology can change rapidly, political and social,
insitutions generally change very slowly. Furthermore, they
almost never change in anticipation of social need, but only
in response to one.

We must also keep in mind the presence of social delays--the
delays necessary to allow society to absorb or to prepare for
a change. Most delays, physical or social reduce the stability
of the world system and increase the likelihood of the
overshoot mode. The social delays, like the physical ones, are
becoming increasingly more critical because the processes of
exponential growth are creating additional pressures at a
faster and faster rate. Although the rate of technological
change has so far managed to keep up with this accelerated
pace, mankind has made virtually no new discoveries to
increase the rate of social, political, ethical, and cultural

Even if society's technological progress fulfills all
expectations, it may very well be a problem with no technical
solution, or the interaction of several such problems, that
finally brings an end to population and capital growth.

Applying technology to the natural pressures that the
environment exerts against any growth process has been so
successful in the past that a whole culture has evolved around
the principle of fighting against limits rather than learning
to live with them.

Is it better to try to live within that limit by accepting a
self-imposed restriction on growth? Or is it preferable to go
on growing until some other natural limit arises, in the hope
that at that time another technological leap will allow growth
to continue still longer? For the last several hundred years
human society has followed the second course so consistently
and successfully that the first choice has been all but

There may be much disagreement with the statement that
population and capital growth must stop soon. But virtually no
one will argue that material growth on this planet can go on
forever. At this point in man's history, the choice posed
above is still available in almost every sphere of human
activity. Man can still choose his limits and stops when he
pleases by weakening some of the strong pressures that cause
capital and population growth, or by instituting
counterpressures, or both. Such counterpresures will probably
not be entirely pleasant. They will certainly involve profund
changes in the social and economic structures that have been
deeply impressed into human culture by centuries of growth.
The alternative is to wait until the price of technology
becomes more than society can pay, or until the side-effects
of technology suppress growth themselves, or until problems
arise that have no technical solutions. At any of those points
the choice of limits will be gone.

Faith in technology as the ultimate solution to all problems
can thus divert our attention from the most fundamental
problem--the problem of growth in a finite system--and prevent
us from taking effective action to solve it.

On the other hand, our intent is certainly not to brand
technology as evil or futile or unnecessary. We strongly
believe that many of the technological developments mentioned
here--recycling, pollution-control devices,
contraceptives--will be absolutely vital to the future of
human society if they are combined with deliberate checks on
growth. We would deplore an unreasoned rejection of the
benefit of technology as strongly as we argue here against an
unreasoned acceptance of them. Perhaps the best summary of our
position is the motto of the Sierra Club : "Not blind
opposition to progress, but opposition to blind progress".

We would hope that society will receive each technological
advance by establishing the answers to three questions before
the technology is widely adopted. The questions are:

- What will be the side-effects, both physical and social, if
this development is introduced on a large scale?

- What social changes will be necessary before this
development can be implemented properly, and how long will it
take to achieve them ?

- If the development is fully successful and removes some
natural limits to growth, what limit will the growing system
meet next? Will society prefer its pressures to the ones this
development is designed to remove?

We are searching for a model that represents a world system
that is:

1. sustainable without sudden and uncontrollable collapse; and

2. capable of satisfying the basic material requirements of
all of its people

The overwhelming growth in world population caused by the
positive birth-rate loop is a recent phenomenon, a result of
mankind's very successful reduction of worldwide mortality.
The controlling negative feedback loop has been weakened,
allowing the positive loop to operate virtually without
constraint. There are only two ways to restore the resulting
imbalance. Either the birth rate must be brought down to equal
the new, lower death rate, or the death rate must rise again.
All of the "natural" constraints to population growth operate
in the second way--they raise the death. Any society wishing
to avoid that result must take deliberate action to control
the positive feedback loop--to reduce the birth rate.

But stabilizing population alone is not sufficient to prevent
overshoot and collapse; a similar run with constant capital
and rising population shows that stabilizing capital alone is
also not sufficient. What happens if we bring both positive
feedback loops under control simultaneously? We can stabilize
the capital stock in the model by requiring that the
investment rate equal the depreciation rate, with an
additional model link exactly analogous to the
population-stabilizing one.

The result of stopping population growth in 1975 and
industrial capital growth in 1985 with no other changes is
that population and capital reach constant values at a
relatively high level of food, industrial output and services
per person. Eventually, however, resource shortages reduce
industrial output and the temporily stable state degenerates.
However, we can improve the model behavior greatly by
conbining technological changes with value changes that reduce
the growth tendencies of the system.

Then the stable world population is only slightly larger than
the population today. There is more than twice as much food
per person as the average value in 1970, and world average
lifetime is nearly 70 years. The average industrial output per
capita is well above today's level, and services per capita
have tripled. Total average income per capita (industrial
output, food, and services combined) is about half the present
average US income, equal to the present average European
income, and three times the present average world income.
Resources are still being gradually depleted, as they must be
under any realistic assumption, but the rate of depletion is
so slow that there is time for technology and industry to
adjust to changes in resource availability.

If we relax our most unrealistic assumption--that we can
suddenly and absolutely stabilize population and capital,
replacing them with the following:

1. The population has access to 100 percent effective birth

2. The average desired family size is two children.

3. The economic system endeavors to maintain average
industrial output per capita at about the 1975 level. Excess
industrial capability is employed for producing consumption
goods rather than increasing the industrial capital investment
rate above the depreciation rate.

We do not suppose that any single one of the policies
necessary to attain system stability in the model can or
should be suddenly introduced in the world by 1975. A society
choosing stability as a goal certainly must approach that goal
gradually. It is important to realize, however, that the
longer exponential growth is allowed to continue, the fewer
possibilities remain for the final stable rate.

Many people will think that the changes we have introduced
into the model to avoid the growth-and collapse behavior mode
are not only impossible, but unpleasant, dangerous, even
disastrous in themselves. Such policies as reducing the birth
rate and diverting capital from production of material goods,
by whatever means they might be implemented, seem unnatural
and unimaginable, because they have not, in most people's
experience, been tried, or even seriously suggested. Indeed
there would be little point even in discussing such
fundamental changes in the functioning of modern society if we
felt that the present pattern of unrestricted growth were
sustainable into the future. All the evidence available to us,
however, suggests that of the three alternatives--unrestricted
growth, a self-imposed limitation to growth, or a
nature-imposed limitation to growth--only the last two are
actually possible.

Achieving a self-imposed limitation to growth would require
much effort. It would involve learning to do many things in
new ways. It would tax the ingenuity, the flexibility, and the
self-discipline of the human race. Bringing a deliberate,
controlled end to growth is a tremendous challenge, not
easiliy met. Would the final result be worth the effort? What
would humanity gain by siuuch a transition, and what would
it,lose? Let us consider in more detail what a world of
nongrowth might be like.

We have after much discussion, decided to call the state of
constant population and capital, by the term "equilibrium".
Equilibrium means a state of balance or equality between
opposing forces. In the dynamic terms of the world model, the
opposing forces are those causing population and capital stock
to increase (high desired family size, low birth control
effectivness, high rate of capital investment) and those
causing population and capital stock to decrease (lack of
food, pollution, high rate of depreciation or obsolescence).
The word "capital" should be understood to mean service,
industrial, and agricultural capital combined. Thus the most
basic definition of the state of global equilibrium is that
population and capital are essentially stable, with the forces
tending to increase or decrease them in a carefully controlled

There is much room for variation within that definition. We
have only specified that the stocks of capital and population
remain constant, but they might theoretically be constant at a
high level or a low level--or one might be high and the other
low. The longer a society prefers to maintain the state of
equilibrium, the lower the rates and levels must be.

By choosing a fairly long time horizon for its existence, and
a long average lifetime as a desirable goal, we have now
arrived at a minimum set of requirements for the state of
global equilibrium. They are:

1. The capital plant and the population are constant in
size.The birth rate equals the death rate and the capital
investment rate equals the depreciation rate.

2. All input and output rates--birth, death, investment, and
depreciation--are kept to a minimum.

3. The levels of capital and population and the ratio of the
two are set in accordance with the values of the society.They
may be deliberately revised and slowly adjusted as the advance
of technology creates new options.

An equilibrium defined in this way does not mean stagnation.
Within the first two guidelines above, corporations could
expand or fail, local populations could increase or decrease
income could become more or less evenly distributed.
Technological advance would permit the services provided by a
constant stock of capital to increase slowly. Within the third
guideline, any country could change its average standard of
living by altering the balance between its population and its
capital. Furthermore, a society could adjust to changing
internal or external factors by raising or lowering the
population or capital stocks, or both, slowly and in a
controlled fashion, with a predetermined goal in mind. The
three points above define a dynamic equilibrium, which need
not and probably would not "freeze" the world into the

Capital configuration that happens to exist at present time.
The object in accepting the above three statements is to
create freedom for society, not to impose a straitjacket.

What would life be like in such an equilibrium state? Would
innovation be stifled? Would society be locked into the
patterns of inequality and injustice we see in the world
today? Discussion of these questions must proceed on the basis
of mental models, for there is no formal model of social
conditions in the equilibrium state. No one can predict what
sort of institutions mankind might develop under these new
conditions. There is, of course, no guarantee that the new
society would be much better or even much different from that
which exists today. It seems possible, however, that a society
released from struggling with the many problems caused by
growth may have more energy and ingenuity available for
solving other problems. In fact, we believe, that the
evolution of a society that favors innovation and
technological development, a society based on equality and
justice, is far more likely to evolve in a state of global
equilibrium than it is in the state of growth we are
experiencing today

Population and capital are the only quantities that need be
constant in the equilibrium state. Any human activity that
does not require a large flow of irreplaceable resources or
produce severe environmental degradation might continue to
grow indefinitely. In particular, those pursuits that many
people would list as the most desirable and satisfying
activities of man--education, art, music, religion, basic
scientific research, athletics, and social interactions--could

All of the activities listed above depend very strongly on two
factors. First, they depend upon the availability of some
surplus production after the basixc human needs of fod and
shelter have been met. Second, they require leisure time. In
any equilibrium state the relative levels of capital and
population could be adjusted to assure that human material
needs are fulfilled at any desired level. Since the amount of
material production would be essentially fixed, every
improvement in production methods could result in increased
leisure for the population--leisure that could be devoted to
any activity that is relatively nonconSuming and nonpolluting,
such as those listed above

Technological advance would be both necessary and welcome in
the equilibrium state. The picture of the equilibrium state we
have drawn here is idealized, to be sure. It may be impossible
to achieve in the form desribed here, and it may not be the
form most people on earth would choose. The only purpose in
describing it at all is to emphasize that global equilibrium
need not mean an end to progress or human development. The
possibilities within an equilibrium state are almost endless.

An equilibrium state would not be free of pressures, since no
society can be free of pressure. Equilibrium would require
trading certain human freedoms, such as producing unlimited
numbers of children or consuming uncontrolled amounts of
resources, for other freedoms, such as relief from pollution
and crowding and the threat of collapse of the world system.
is possible that new freedoms might also arise--universal and
unlimited education, leisure for creativity and inventiveness,
and, most important of all, the freedom from hunger and
poverty enjoyed by such a small fraction of the world's people

We can say very little at this point about the practical, day
by-day steps that might be taken to reach a desirable,
sustainable state of global equilibrium. Neither the world
model nor our own thoughts have been developed in sufficient
detail to understand all the implications of the transition
from growth to equilibrium. Before any part of the world's
society embarks deliberately on such a transition, there must
be much more discussion, more extensive analysis, and many new
ideas contributed by many different people.

The equilibrium society will have to weigh the trade-offs
engendered by a finite earth not only with consideration of
present human values but also with consideration of future
generations. long-term goals must be specified and short term
goals made consistent with them.

We end on a note of urgency. We have repeatedly emphasized the
importance of the natural delays in the population-capital
system of the world. These delays mean, for example, that if
Mexico's birth rate gradually declined from its present value
to an exact replacement value by the year 2000, the country's
population would continue to grow until the year 2060. During
that time the population would grow from 50 million to 130
million. We cannot say with certainty how much longer mankind
can postpone initiating deliberate control of its growth
before it will have lost the chance for control. We suspect on
the basis of present knowledge of the physical constraints of
the planet that the growth phase cannot continue for another
one hundred years. Again, because of the delays in the system,
if the global society waits until those constraints are
unmistakably apparent, it will have waited too long.

If there is cause for deep concern, there is also cause for
hope. Deliberately limiting growth would be difficult, but not
impossible. The way to proceed is clear, and the necessary
steps, although they are new ones for human society, are well
within human capabilities. Man possesses, for a small moment
in his history, the most powerful combination of knowledge,
tools, and resources the world has ever known. He has all that
is physically necessary to create a totally new form of human
society--one that would be built to last for generations. The
two missing ingredients are a realistic, long-term goal that
can guide mankind to the equilibrium society and the human
will to achieve that goal. Without such a goal and a
commitment to

it, short-term concerns will generate the exponential growth
that drives the world system toward the limits of the earth
and ultimate collapse. With that goal and that commitment,
mankind would be ready now to begin a controlled, orderly
transition from growth to global equilibrium.

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Richard Moore (rkm)
Wexford, Ireland

"Escaping The Matrix - 
Global Transformation: 
    "...the Patriot Act followed 9-11 as smoothly as the
      suspension of the Weimar constitution followed the
      Reichstag fire."  
      - Srdja Trifkovic

    There is not a problem with the system.
    The system is the problem.

    Faith in ourselves - not gods, ideologies, leaders, or programs.
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