The Pareto Principle, aka the “80/20 Rule”, states that 80% of the output is generated by 20% of the input.
For example, in any given academic department of engineering, 20% of the faculty generates 80% of the papers, research funding, graduated students, citations, or whatever metric. And 100% of the faculty will tell you they are in that 20% for all metrics.
You’ll see the 80/20 rule throughout OpenSees as well.
20% of contributors wrote 80% of the code.
20% of the code is responsible for 80% of the computations and (a mostly different) 20% of the code is responsible for 80% of the bugs.
20% of the users ask 80% of the questions and 20% of the community answers 80% of those questions.
Beyond anecdotes, the 80/20 rule can help you optimize your OpenSees experience. Find the top 20% of element and constitutive models that you use. If you then spend some time to research, understand, test, and ask about those models, you will eliminate 80% of your future OpenSees modeling errors and frustrations.