s-curves (Theodore Modis)

 
Theodore Modis., Prediction : society's telltale signature reveals the past and forecasts the future, 1992.

written by Theodore Modis 

pp.37-38
p.37
  Critics of S-curves have always raised the question of uncertainties as the most serious argument against forecasts of this kind.  
p.37
Obviously the more good-quality measurements available, the more reliable the determination of the final ceiling.  But I would not dismiss the method for fear of making a mistake.  
p.37
Alain Debecker and I carried out a systematic study of the uncertainties to be expected as a function of the number of data points, their measurement errors, and how much of the S-curve they cover.
p.37
We did this in the physics tradition through a computer program simulating “historical” data along S-curves smeared with random deviations, and covering a variety of conditions.  The subsequent fits aimed to recover the original S-curve. 
p.37
We left the computer running over the weekend. 
pp.37-38
On Monday morning we had piles of printout containing over forty thousand fits.  
p.38
The results were published,12  and a summary of them is given in Appendix B, but the rule of thumb is as follows:

  If the measurements cover about half of the life cycle of the growth process in question and the error per point is not bigger than 10 percent, nine times out of ten the final niche capacity will turn out to be less than 20 percent away from the forecasted one. 

p.38
The results of our study were both demystifying and reassuring.  The predictive power of S-curves is neither magical nor worthless. 

p.38
Bringing this approach to industry could be of great use in estimating the remaining market niche of well-established products with quoted uncertainties.  Needless to say life is not that simple.
products are not sufficiently differentiated, they are sharing the niche with others, in which case the combined populations must be considered. 

p.38
Like any powerful tool, it can create marvels in the hands of the knowledgeable, but it may prove deceptive to the inexperienced. 


p.50
1340
This date [1340] can be considered as the time when the exploring process originated, the moment when Europe's need to explore the West was born.  For the best agreement between curve and data, the early-missing-data parameter has to take a value around fifteen (15). 
pp.50-51
  The conclusion is that there must have been about fifteen (15) attempts before Columbus that failed while trying to explore the West, the first one dating back to around 1340. 
p.51
This kind of backcasting ── if somewhat daring ── is not different from the usual forecasting approach.  We are dealing with a pattern similar to that of the growing vocabulary of an infant if we only look at the data pattern upside down and let time run backward.  The uncertainties on the number fifteen (15) can be estimated (see Appendix B) to be plus or minus three. 

p.57
The first computer model I tried turned out to be a showcase, one of Digital's early successful minicomputers, the VAX 11/750.  The cummulative number of units sold is shown at the top of Figure 3.1.  An S-curve passes quite closely to all twenty-eight trimesterly data points.  In the lower graph we see the product's life cycle, the number of units sold each trimester.  The bell-shaped curve is the  life cycle as deduced from the smooth curve at the top.
p.57
  When I produced this graph in 1985, I conclude that the product was phasing out, something that most marketers opposed vehemently at the time.  They told me of plans to advertise and repackage the product in order to boost sales.  They also spoke of seasonal effects, which could explain some of the recent low sales. 
p.57
  The data points during the following three (3) years turned out to be in agreement with my projections.  To me this came as evidence that promotion, price, and competition were condition present  throughout  a product's life cycle and have no singular effect.  The new program that marketers put in place were not significantly different from those of the past and therefore did not produce a modification of the predicted trajectory. 

p.83
What is unique about Shelley's case, however, is that he died leaving his work largely unfinished.  The ceiling of the curve indicates a creative potential of twice the number of poems written (Appendix C, Figure 4.3).  Apparently, when Shelley died he had said only half of what he would have said, and in his case, his accidental death was unnatural. 
  I was glad to have done Shelley's curve when I saw Marchetti again at the 1989 International Conference on Diffusion of Technologies and Social Behavior.  During a coffee break he explained to the swarm of fans who usually surround him that people die when and only when they become exhausted of creativity, even if their death may look like suicides or accidents.  “There are no accidents”, he proclaimed.  I promptly confronted him with Shelley's case.  He did not argue.  He was willing to allow for exceptions.  As walked away I heard someone say, “Here is a way for life insurance companies to determine whether an accident is real or not before they decide to pay up!”

p.98
Today, cardiovascular ailments claim the largest share, close to two-thirds of all deaths, with cancer second at about half that number.  A hundred years ago pneumonia and tuberculosis were running ahead of cancer. 

p.109
  To take another example, more recently steam locomotives were replaced by diesel or electric ones in most parts of the world.  
p.109
In his book, The Rise and Fall of Infrastructures, Arnulf Grubler shows that the percentages of steam locomotives in the United States and the U.S.S.R. declines just as the percentage of horses had done earlier.  The raw data outline an S-curve so clearly that there is no need to fit them with a curve (Appendix C, Figure 6.1). 
p.109
  The data also show that the Russian and American steam engine decline curves are ten years apart but strictly parallel.
p.109
This similarity is deceptive, however, because of another substitution that was taking place.

p.109
... but their dependence on railways is fundamentally different.  By 1950, mid-way through the phasing out of steam in the United States, transportation by railway seemed to have already yielded to road (highway) transport, with seven times more roadway length than railway track (see Chapter Seven). 


p.112
  Consider the following hypothetical case.  You are concerned about the new hamburger stand that opened recently across the street from yours. 
p.112
To make it easy, let us also suppose that the stand across the street has set up a public counting device which advertises the number of hamburgers it has sold so far. 
p.112
  It is easy to find out if your competitor's way is going to be the way of the future.  Here is a recipe.  Start your own count of how many hamburgers you have sold since the competition appeared and track the ratio ── your competitor's number divided by your number.  Then run to a stationary store and buy some semilogarithmic graph paper on which you will have enough data points to discern the trend.  If the data points form a straight line (within the small daily fluctuations, of course), you may want to start looking around for another business.  If, on the other hand, the trend is flattening or the pattern is such that no overall straight line is discernable, then chances are the guys across the street are not here to stay, or if they are, they will not take all the business. 


p.219
  No, there are things to be done and those who market products do them most of the time, but they believe they are shaping the future, while in reality they are only compensating for changes in the environment in order to maintain the established course.  They are reacting to change in the same way a biological system would in nature.  Whenever there is a danger of falling behind the established path, they bring out good ideas from manufacturing, product design, and advertising.  These ideas may have been dormant for some time; they are called upon as needed.  This is how it happens in biological systems.  Mutants are kept in a recessive state until a change in the environment brings them into the foreground. 

p.219
sweating and shivering help regulate the temperature of the body. 

p.219
Innovation and promotion do not create new markets.  They are part of the competitive struggle, which becomes more and more important as growth processes saturate, and the only to way to maintain “healthy” growth is by taking the food from a competitor's mouth. 


p.221
If “decision makers” became more aware of well-established natural-growth processes and of how much free choice they may not have after all, they would benefit not only from reduced stress but also from the avoidance of mistakes.  

p.224
  Once growth is complete, the level reached reflects an equilibrium.  Its signature becomes an invariant or constant that, despite erratic fluctuations, 

p.224
existence of tolerance thresholds 

p.225
When these tools are grasped more than just intellectually, they give rise to a better understanding of the most probable evolution of a process and how much of it still lies ahead.  Such understanding goes well beyond the supertanker analogy, which claims that supertankers cannot make sharp turns, and therefore their immediate course is predictable. 

p.225
From half of a growth process one can intuitively predict the other half. 

p.234
Appendix B
Expected Uncertainties on S-Curve Forecasts 

p.235
In other words, a slower rate of growth correlates to a larger niche size, and vice versa.  This implies that accelerated growth is associated with a lower ceiling, bringing to mind such folkloric images as short life spans for candles burning at both ends. 

p.279
9.  Historical Statistics of the United States, Colonial Times to 1970, vols. 1 and 2, Bureau of the Census, Washington, DC.

11.  Arnulf Grubler, The Rise and Fall of Infrastructures (Heidelberg: Physica Verlag, 1990), p. 189.

12.  Cesare Marchetti, “Primary Energy Substitution Models: On the Interaction between Energy and Society”, Technological Forecasting and Social Change, vol.1 (1977): 345-56.  This paper was first delivered in Moscow in November 1974 and published in the August 1975 issue of Chemical Economy and Engineering Review (CEER). 

  (Prediction : society's telltale signature reveals the past and forecasts the future / Theodore Modis.,  1. forecasting., 2. creation (literary, artistic, etc.)., 3. science and civilization.,  CB 158.M63, 303.49--dc20, 1992, )
‘’•─“”
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