Here's a rather obscure window in GP that I don't see used often. Go Cards>Inventory>Item History to view.
* click image to enlarge
As you can see, this window provides a wealth of historical information about the sales and usage of your items, by period, by year.
Additionally, if you're running MRP or using the PO Generator in GP, this window can be used to enter forecast usage of items for planning purposes. Access this window and click on the Help icon for more infomation.
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