Thoughts on the change rate of class and Assembly and the reasons for changes

We are constantly dealing with classes and assemblies every day. I wonder if you have noticed the change rate of a class or assembly?

If you pay attention to it, you will find that in excellent solutions, the change rate of class and assembly is also hierarchical; the more core, the less relevant to the business, the smaller the probability of changes, the more peripheral and business-related it is, the higher the probability of changes; the change rate and reasons of the class in each assembly should be consistent, this kind of assembly is more stable.

So what are the rules of change rates and causes of changes for members in each class?