- There are important segmentation or types of inventory.
- There is a segmentation of inventory that includes the types of inventory, inventory classification, and the uses of inventory.
- The functions of inventory include the anticipation inventory, goods in transit or stock in transit, transportation inventory, pipeline inventory, lot size inventory and hedge inventory or speculative inventory.
Introduction to Inventory Segments
In this article, we will cover many of the different ways that inventory can be divided or segmented.
The Concept of Types of Inventory, Inventory Types, Categories of Inventory, Inventory Categories and Inventory Classification
There are many concepts of the types of inventory, inventory types, categories of inventory or inventory categories that are used in supply chain management. Some of these have to do with how the types of inventory or inventory types are treated by the supply planning system. For instance, high-value product inventory may be set on different supply planning settings that low-value product inventory.
Categories of inventory or inventory categories can be based upon what that inventory does. That is, is the inventory a raw material, a finished good, a component, work in process, etc. Understanding these categories of inventory is important both for working with others (so you can have a shared understanding of the meaning of different categories of inventory) but also to decide which of the inventory categories one may want to use themselves.
Target Stocking Level, Safety Stock Level, and the Initial Stock Level
One way of looking at inventory is the total amount of inventory in the system or the inventory at a stocking location in total. This can be viewed as the actual inventory versus the target inventory.
The target inventory or target inventory level is often made up of the following conceptual components.
- TSL: The Target Stocking Level
- SS: The Safety Stock Level
- ISL: The Initial Stock Level
Each of these different stocks is shown in the following graphic:
- Using this inventory optimization construct, a portion of the total stocking level is the safety stock, and another portion is called the ISL or initial stocking level.
- The initial stocking level would be the target stocking level if no supply or demand variability were to exist.
Segmentation Of Inventory by Inventory Usage
- Inventory has multiple inventory uses.
- It can be categorized into multiple inventory types.
- By categorizing inventory and evaluating the allocation of the overall inventory into the different uses and types, one can gain a measure of the relative impact on overall inventory of these segments.
- It is also valuable to consider what the actual function is the inventory that is carried.
Types of Inventory, Inventory Classification, and Inventory InfoGraphic
The following infographic shows the types of inventory and inventory classification by two different dimensions.
Functions of Inventory: Anticipation Inventory, Goods in Transit or Stock in Transit, or Transportation Inventory, Pipeline Inventory, Lot Size Inventory and Hedge Inventory or Speculative Inventory
Another way to categorize inventory is by its function.
- Fluctuation Inventory: Fluctuation inventory is inventory that is carried to account for variability in either demand or supply. The technical definition of this is safety stock.
- Anticipation Inventory: Anticipation inventory is inventory that is held in anticipation of specific or unusual demand. It goes without saying that all inventory is “anticipatory” in nature unless the stock has been sold already, but what makes anticipation inventory different from normal inventory is that there is a reason that can be pointed to for carrying more inventory than normal. A very common example of anticipation inventory is inventory carried specifically for weather events.
- Goods in Transit, Stock in Transit or Transportation Inventory: Goods in transit, stock in transit or transportation inventory is stock that is somewhere in the process.
- Pipeline Inventory: Pipeline inventory is a subset of transportation inventory. However, pipeline inventory is only the portion of the stock in transit inventory that it is outbound to the customer.
- Lot Size Inventory: A lot size is an order size that in many cases are larger than the demand. The lot size is applied to keep companies from purchasing in “non-economic” quantities, which means quantities that would incur overly high transaction costs. The resultant lot size inventory, therefore, is the inventory that is carried not because of need, but because the lot size required the quantity to be increased. Lot size inventory is differentiated from inventory that is purely demand driven.
- Hedge Inventory or Speculative Inventory: Hedge inventory or speculative inventory is inventory that is carried above what would ordinarily be carried to meet the demand for a speculative purpose. If an entity were to conclude that some input material has a high chance of becoming more expensive in the future, then it would make sense for that entity to purchase and carry hedge inventory or speculative inventory which would reduce its cost of material acquisition. Hedge inventory or speculative inventory would tend to be the most common in raw materials, as the raw material can be converted into so many output items and never really becomes obsolete.
Classes of Inventory: Raw Materials Inventory and Raw Materials Examples, Components Inventory, Work in Process Inventory, Finished Goods Inventory
Another way to classify inventory is of its class.
- Raw Materials Inventory: Raw Materials Inventory is the material that is in a very basic stated with little manufacturing or other processing performed by the supplier. Raw materials examples are things like gold, copper, grain, industrial powders, raw milk, etc. Raw materials examples will tend to be shipped in bulk.
- Component Inventory: Component inventory is inventory that is a recognizable part or assembly that goes into the finished goods. When component inventory is held until a sales order is received, this is called assemble to order manufacturing.
- Work In Process Inventory: Work in process inventory is material that has is somewhere along in the manufacturing process but is not yet a finished good or finished product.
- Finished Goods Inventory: Finished goods inventory may be in storage at the factory right after manufacture, or finished goods inventory can be anywhere in the outbound supply chain. For entities that distribute an item rather than manufacture an item, these entities receive finished goods inventory from suppliers.
Most supply planning systems will not break out the total inventory by the types of inventory that I have listed above.
There are many “dimensions” by which one can “segment” inventory. This article explained some of the most commonly used.
Brightwork MRP & S&OP Explorer
Safety Stock and Service Level Book
Important Features About Safety Stock
How Systems Set Safety Stock
The vast majority of systems allow the setting of safety stock by multiple means (static, dynamic, adjustable with the forecast in days’ supply, etc..). However, most systems do not allow the safety stock to be set in a way that is considerate of the inventory that is available to be applied.By reading this book you will:
- Understand the concepts and formula used for safety stock and service level setting.
- Common ways of setting safety stock.
- Service levels and inventory optimization applications.
- The best real ways of setting both service levels and safety stock.
Chapter 2: Safety Stock and Service Levels from a Conceptual Perspective
Chapter 3: The Common Ways of Setting Safety Stock
Chapter 4: The Common Issues with Safety Stock
Chapter 5: Common Issues with Service Level Setting
Chapter 6: Service Level Agreement
Chapter 7: Safety Stock and Service Levels in Inventory Optimization and Multi-Echelon Software
Chapter 8: A Simpler Approach to Comprehensively Setting Safety Stock and Service Levels