Uneven development of system elements

This is an interesting and surprising principle, which can be defined thus  

An engineering system improves monotonically, but the evolution of its individual subsystems follows their own various S-curves. 

The first part of this principle describes how an engineering system improves. It is a monotonic process with periods of nonimprovement, or stagnation, when improvements do not temporarily take place however, the system never retreats. During periods of war and recession, the development of many systems is delayed, and there are no improvements. However, we practically never see the worsening of important characteristics of engineering systems, although rare exceptions can be found. 

For example, when cars are considered, usually each year we see not only more attractive cars, but also more efficient, safe, and comfortable ones with respect to the previous generation. However, it is not unusual that during times of crisis, less expensive car models are introduced, and these may come with less expensive and sophisticated suspension or tires. That may lead to worsening of the handling characteristics when compared with their predecessors. Obviously, the more expensive and better models will be introduced again as soon as the crisis is over, and the anomaly will disappear. 

The described phenomenon can be summarized by saying that the entire system has its own life but that all its individual subsystems have their own lives too. There is one S-curve for the entire system and many different S-curves for all subsystems. This pattern has great significance when trying to understand various phenomena from the past but also when trying to prevent their occurrence in future systems. 

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