I had to look at my data....
We have a little over 100 suppliers per authorized purchasing agent. However, 20% of the suppliers processed 80% of purchase orders.
This is for MRO/Direct materials for a non-automotive manufacturing company. This also includes VMI material, as well.
However, we are a classically understaffed organization. In our organization (as compared to other sites), we would need 1-2 more buyers to bring this facility down to other facilities efficiency levels.
We manage because we're all very experienced, very motivated individuals.