From Forrester’s World Dynamics

September 18, 2016

The first half of the book is roughly a documentation of the model being simulated. I didn’t complain because of an early warning that conventional birth control will prove to have little effect on improving the final undesirable equilibrium compared to that without, a method I had imagined as a silver bullet to today’s major world problems.

In the result discussion chapter, I found out I wasn’t entirely wrong about my favorite method. The usual birth control programs do not set a constant birth rate, but which is subject to influences from other variables such as material standard of living, pollutions etc, manifested by their corresponding multipliers. That’s why the simulations faithfully report that with a transient rise of standard of living following a birth control policy, the incentives for increasing birth rate becomes even stronger. This result forces me to clarify myself that what I actually mean by birth control is to set a rigid birth rate independent of other system variables, which might require something like the womb system in Ergo Proxy on the implementation side, as my totalitarian nature quietly creeps up1.

Another thing I shall bear in mind is that there are other modes of disasters that cannot be suppressed by reduced population alone. In fact, the author views capital investment and pollution as primary leverage points and birth control the secondary tool – not the other way around as is my belief. I never really understand what capital investment means as I never comprehended money and its movement. Let’s say that it’s directly associated with industrialization. Then based on the assumptions of this model, the simulation result indicates that fewer people does not lead to hampered capital investment. Consequently pollution comes out to be the destroying force. Therefore birth control even in my stricter definition is not the silver bullet. A comprehensive program exercising self-restraint on multiple fronts including not only reproduction but also economic development, emerge as an attractive idea.

Recall that this is the state-of-the-art in 1970, it amazes me to see that people today are still spouting the ugly idea that technology is the savior of mankind. And I’m more ashamed of myself than amazed at them that I didn’t see the fallacy until the book clearly spells it out. In contrast to this indifference that new insights were received with, ancient ideas such as self-discipline have never been adopted by the mainstream either. I see traces of environmentalism in Greek mythology already, as the Greeks were temporarily confined in a small world centered around Greece so the transition from golden to bronze ages mostly as a result of human multiplication were perceived; certainly there were a couple of great Chinese thinkers who ages ago saw through the vanity of the rushing and blindly excited expansionists, tech-enthusiasts, growthists2… Oh yeah, there certainly is a possibility that we can escape from the confinement of the earth and continue to grow in some other earth-like planets. But it’s exactly those who insist in letting expansion go unchecked and willingly accept the consequential rising violence and danger of war as fated – some of whom by the way I personally know (!) – that are diminishing this possibility of space exploration by diverting huge funds to the defense causes.

Just to add some seasonal flavor to this crude write-up – as I’m visiting my parents, I’ll briefly mention that dad staunchly rejected the notion of crowding induced expansion – in that classical way of leaving me with plenty of sour feelings. He cited the Japanese as an example saying Tokyo is one of the cities with highest density, yet their citizens are more civil than most and they’re doing just fine. That can be explained by a degradation of quality of life, or if it’s a conscious choice then it’s equivalent to self-restraint, now not on reproduction or urbanization, but on personal space – a kind of self-restraint that requires more social compromise. Ultimately, there is a mathematical upper bound of crowding level that is everybody having exactly the space to stand upright, beyond which one cannot hope to live unless some sort of expansion is employed, regardless of a horizontal or vertical one.

Now, I’m not entirely without reservation regarding this model. About the multipliers mentioned earlier, they are invariably single-variable functions of the form f(x). One can easily hypothesize that a more reasonable form would be f(x,y,…), if introducing multipliers itself is a reasonable enough thing to do in the first place. The latter doubt is elicited by comparing models in this book and in the ecology literature to those derived for physical or mechanical systems. The equations for a mechanical system is obtained by applying the laws of conservation. No matter what approximation treatment one has to take in order to carry on, it always feels reassuring to recall that the system is a lawful descent of a noble origin. On the contrary, when constructing a model for the world system, there seems to be no similar principles to adhere to. So we wildly resort to artificial multipliers based on observations of relationships among a limited set of variables, which introduce high order nonlinearities that may be unnecessary. I don’t like it. But it’s been nearly five decades since the book’s publication. There are newer editions and organized research. People must have come up with more elegant ideas.

Irrespective of model uncertainties, the next question would naturally be concerned with deriving a control law to bring the nonlinear system into a desired equilibrium, or even an acceptably oscillatory steady-state. After all, what brought me in touch with this book is Aström’s review paper3. Despite the fact that the equation numbering runs to 45 and that the world system chart in the back cover seems much complicated, there are in effect five states: population, pollution, capital investment, natural resources and fraction of capital devoted to agriculture. So the system order is merely n=5, not a scary number at all, is it? The control performance may then be quantified by quality of life which is a function of these states. I immediately realize the difficulties on the sensor side of the problem. Anyway, I wonder what has been done towards control of the world system.

As a final word, I must reiterate to myself that this is indeed a 50 year-old result. One of the interesting concepts that until now never formally entered my consciousness is stated in 3.27 Capital-Investment Discard CID as follows:

It also includes education and the results of scientific research … and the investment in them decays at about the same rate as for physical capital.


[1] That was a joke.. Going through the normal democratic way is preferable, for I’m not particularly concerned either if it takes longer than it’s too late to alter the course.
[2] I understand this word does not formally exists. Just throwing out whatever title I despise.
[3] Aström, K. and Kumar, P., Control: A perspective, Automatica, vol. 50(1): 3-43, 2014.

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