Are you looking for **"degree of stability"**?  

Fixed or variable cost stability.

>- [**stability**](https://www.collinsdictionary.com/dictionary/english/stability) - "resistance to change"
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> e.g. "a **degree of stability** becomes a linguistic variable assuming terms such as “unstable”, “weakly stable”, “more or less stable”, “strongly stable”, “completely stable ...[**1**](https://books.google.com.br/books?id=uo-6BQAAQBAJ&pg=PA231&dq=%22degree+of+stability%22&hl=pt-BR&sa=X&ved=0ahUKEwig2YKpqbzgAhXkCtQKHUv8DiAQ6AEISzAF#v=onepage&q=%22degree%20of%20stability%22&f=false)