Following the discussions here, I found that it could benefit from a better understanding what the Pareto principle is generally good for and what it is not. So here are my thoughts.<p>The Pareto principle is useless if considering just a specific predetermined goal in isolation. If I want to climb to the top of a mountain, I have to climb 100 % of the height. Then it makes no practical difference, when I know that I can reach 80% of the height in 20% of the time, for example. However, the Pareto principle encourages us to (re)evaluate a goal in the light of limited resources. Is it better to be satisfied with only climbing 80% of the height of the mountain and use the time saved for other activities that I would otherwise miss out on? The answer to this question depends on other more general goals that I am pursuing.<p>Applied to software development, this tells us that we should consider for example implementing certain features or striving for a certain level of quality not as goals in themselves, but as framed by more fundamental goals. It is therefore no wonder that given the same code base, the immediate goals what to do next can differ greatly depending on what the fundamental goals are, such as earning money vs. having fun vs. taking pride in, etc. (they may align by coincidence, though). The Pareto principle helps us to (re)evaluate and compare immediate goals in the light of such fundamental goals: Is it better to implement feature A completely and dispense with feature B, or is it better to implement a simplified feature A´ and have room for a simplified feature B´ in the same timeframe (in this example the limiting resource)? Here, the fundamental goal is implicit in the utility function indicated by the word "better", in our example better according to earning money vs. better according to having fun vs. better according to taking pride in, etc.<p>Of course, considering the Pareto principle when (re)evaluating immediate goals does not gurantee to arrive at the best conclusion. And there are additional considerations outside the Pareto principle, such as short-term goals competing with long-term goals under the same fundamental goals, or legal obligations that are non-negotiable. Here, we enter the sphere of policies, where the policy makers decide upon regulations beyond the individual fundamental goals. In practice we have a hierarchy of multiple goals. On each hierarchy level the Pareto principle is still worth considering as long as there are conflicting goals and limited resources.<p>To recapitulate: The Pareto principle can only be applied meaningfully when evaluating certain alternative goals according to a given utility function for one or more specific limited resources.