Thursday, August 21, 2008

Sporadic Usage Items

In many organizations more than 50% of stocked products have sporadic usage – that is, they are not sold or used on a regular, predictable basis. In other words you have no idea when they will be sold or used. In previous articles we have suggested that you base the inventory of sporadic usage products on a multiple of the normal or typical order quantity. For example, if you normally sell or use two of the items in a transaction, you would set the "target" stock level equal to two pieces (if you wanted to maintain one transaction in stock) or four pieces (if you wanted to maintain two transactions in stock).

You might think that like recurring items, the average or ideal value of sporadic inventory items should be some average of the normal quantity on hand, perhaps the target stock level divided by two. But because sporadic usage items are not consumed or sold on a predictable basis, it is very difficult to calculate an "average" investment for these items. After all, you might have the two or four pieces of a sporadic usage item in stock for a week, a month, or for more than a year! Therefore we have to consider the "ideal" value of sporadic inventory items to be equal to the target stock level quantity times the average cost. It's true that because we will occasionally use some of the stock of some sporadic items, the value of the target inventory will overstate the average value of some items. But this is the most accurate method we know of determining the ideal value of sporadic inventory items.
Unfortunately the value of the inventory of a sporadic inventory item will often exceed the value of the target stock level. Why? Because you may have to order a vendor package quantity of a product when replenishing stock. And the vendor package quantity may not have any relationship to the normal customer order quantity. For example, say that the normal customer order quantity of a product is three pieces and we want to maintain two normal order quantities in stock. The target stock level is six pieces (2 orders x 3 pieces per order). Whenever the replenishment position of the item falls below six pieces, a replenishment order is issued. If we must order a vendor package of 10 pieces, the product's stock level after we receive the replenishment shipment will probably be greater than the target stock level of six pieces.Because sporadic inventory is not sold on a recurring basis, we must carefully monitor the value of any amount of sporadic inventory in excess of the target stock level, particularly for those items with a high unit cost. We can define "planned excess" of sporadic inventory items as a quantity equal to:

(Target Stock Level - Normal Order Quantity) + Vendor Package Quantity

One of our goals should be to minimize the value of this planned excess. If a sporadic inventory item has a high planned excess value consider:
* Ordering an amount of the product close to the normal order quantity, even if you have to pay a higher price per unit.
* Discontinuing the product from stock inventory and ordering it only as necessary to fill specific requirements.
* Sharing one vendor package quantity among several stocking locations.
* Substituting a slightly more expensive item without passing the additional cost to the customer. Saving the carrying cost of excess inventory of one sporadic inventory item may more than compensate from the reduced profit on the resulting sale.

One of the best inventory metrics involves comparing the value of your current inventory to the sum of the values of the ideal stock level for each product. If the values are not close to one another, your buyers or inventory planners are probably not following the replenishment recommendations generated by your computer system. Are the system recommendations inadequate to provide your desired level of customer service and inventory turnover? Or do your buyers need more training in using your system to help your company maximize the return you receive from your investment in inventory? Either way, comparing your actual inventory to the "ideal" will lead you to action that can lead to improved profitability.

In our next article we will explore what you can do if your calculated ideal stock level is too high and needs to be reduced in order to achieve your organization's inventory turnover and profitability goals.

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