Such experience of events is always in the past and presents some unavoidable difficulties if used as a means of prediction. If events occur, on the average, every ten years, a very considerable period of time is required, say 50 years, to produce a statistically significant record of events for analysis. During this time, the factors that gave rise to the past events may have changed completely, while other new factors not covered by past recorded experience may have been introduced. Thus accumulated experience may be invalid or inadequate as a basis for establishing probabilities of future events. Some persons, including a few building officials, approach the matter of regulating for safety with a zeal that demands perfection.
Building involves the greatest set of compromises with which man is regularly faced.
It is inevitable that safety should be involved. In a conservative approach, one would rule out all innovations simply because it is not known whether they will create some hazard. If innovation is allowed, one will always be defeated by the events the human mind is unable to predict. It cannot be argued seriously that all innovations should be accepted automatically until experience shows that they constitute some hazard. A building code must impose some restriction, but it should also accept a reasonable probability of failure.