An important source of uncertainty, Techniques of Systems Analysis notes, is degradation of estimated performance:
Notice we said degradation, not variation.
The reader is undoubtedly familiar with examples of this effect. For instance one might ask a porter what his average tip is. He answers $2.00. You give him $2.00 and he says, “First time anybody came up to my average.”
It should be understood that most of the estimates of average performance are of this sort. They are goals, often idealized and optimistic goals, rather than sober predictions. We are talking here about more than the (very important) question of the degradation of performance of individual soldiers and organizations. The Systems Analyst is equally concerned with the degradation of performance of equipment undergoing Research and Development as compared to the predictions of the designers. It is amazing how uniformly optimistic most of the contracts and official sources seem to be — at least for the short term estimates. For the long term the same sources tend systematically to underestimate long term improvements.
There is another aspect of the degradation of our performance which is of extreme importance. It is related to or identical with the “battleship thinking” of the prewar Navy. The battleship was a fine object in its day but, when it day had passed, some of our naval officers were reluctant to give it up. They placed a reliance on it which proved to be costly.