The bigger the gap between what you have and what you actually use also impacts the cost and quality of the process. It will take longer to find what it is you actually want and wrong selections will be more common.
7. How many customers / vendors / stock / or whatever (relevant for process) produce 80+% of volume
The fewer of something you have making up the top 80% the easier the process will be to improve.
If you have 5000 customers it becomes daunting, but if you start with the top 100 you have an achievable target. Also it will get to the point where the marginal gain is not worth the effort. If some one trades with you only once or twice a year you may still want them as a customer but will want a simple, trouble free way of dealing with them.