Thursday, August 21, 2008

Inventory shrinkage and obsolence

Shrinkage and obsolescence includes any stock material that is purchased but not sold, used to provide a service, or is part of an assembly or finished good. This includes material that is lost, stolen, broken, scrap, or becomes obsolete in our warehouse. Some products are more susceptible to shrinkage and obsolescence than other items. We need to determine factors for these two important components of the carrying cost.

To calculate a shrinkage factor for a specific item, divide the total amount of adjustments due to shrinkage (material lost, stolen, broken, or considered scrap) recorded in the past 12 months by the total stock receipts for the product during the same time period. Why don't we use the average inventory value in this calculation? Because all inventory adjustments are already reflected in the average inventory value. We want to determine how much of the total quantity of the inventory that was received could not be sold, used in production, or used to service a customer. Many companies calculate a shrinkage factor for an entire product line, rather than for individual items. This allows a shrinkage factor to be applied to products that have not yet been inventoried for a full 12 months.

To get an accurate obsolescence factor, we usually have to use a longer time period. For example, if you normally consider inventory obsolete after it has been in your warehouse for 12 months, you might want to divide the amount of write-off adjustments made this year by the total amount of stock receipts for the item last year. Why? Because any material written off due to obsolescence this year was probably received last year. Again, it might be more meaningful if you calculate an obsolescence factor for an entire product line rather than an individual product.If you don't liquidate obsolete inventory on an ongoing basis, you may also want to vary the time periods you consider in this analysis. For example, one of our customers had a large obsolescence write-off last year that covered material that had been received anywhere from two to five years ago. To calculate their write-off factor, we divided the amount of adjustments due to obsolescence over the past two years by the total amount of stock receipts recorded in that two- to five-year period.

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