Use your newsagency software to compare suppliers that compete in a department or category. Do this based on brand even if all are through one wholesales, like pens.
Compare the performance of Artline, Pilot, Bic and Uniball, see which provides the better stock turn, return on space and ROI.
Compare your suppliers and focus more on those that perform better for you.
Your data is more important to your business that data from your suppliers about what they have sold to you.