ABC analysis

Last updated

In materials management, ABC analysis is an inventory categorisation technique which divides inventory into three categories: 'A' items, with very tight control and accurate records, 'B' items, less tightly controlled and with moderate records, and 'C' items, with the simplest controls possible and minimal records. An ABC analysis provides a mechanism for identifying items that will have a significant impact on overall inventory cost, [1] while also providing a mechanism for identifying different categories of stock that will require different management and controls.

Contents

The ABC analysis suggests that inventories of an organization are not of equal value. [2] Thus, the inventory is grouped into three categories (A, B, and C) in order of their estimated importance. 'A' items are very important for an organization. Because of the high value of these items, frequent value analysis is required. In addition to that, an organization needs to choose an appropriate order pattern (e.g. "just-in-time") to avoid excess capacity. 'B' items are important, but less so than 'A' items, although more important than 'C' items. Therefore, 'B' items are intergroup items. 'C' items are marginally important.

ABC analysis categories

There are no fixed thresholds for each class, and different proportions can be applied based on objectives and criteria which vary between companies. [3] ABC analysis is similar to the Pareto principle in that the 'A' items will typically account for a large proportion of the overall value, but a small percentage of the number of items. [4] Examples of ABC class are:

Another recommended breakdown of ABC classes: [5]

  1. "A" approximately 10% of items or 66.6% of value
  2. "B" approximately 20% of items or 23.3% of value
  3. "C" approximately 70% of items or 10.1% of value of the items

ABC analysis in ERP packages

Major ERP packages have built-in function of ABC analysis. User can execute ABC analysis based on user defined criteria and system apply ABC code to items (parts).

In the absence of an ERP system, ABC Analysis can also be done in MS Excel.

Mathematical calculation of ABC analysis

Computed (calculated) ABC analysis delivers a precise mathematical calculation of the limits for the ABC classes. [6] It uses an optimization of cost (i.e. number of items) versus yield (i.e. sum of their estimated importance). Computed ABC was, for example, applied to feature selection for biomedical data, [7] business process management [8] and bankruptcy prediction. [9]

Example of the application of weighed operation based on ABC class

Actual distribution of ABC class in the electronics manufacturing company with 4,051 active parts.

Distribution of ABC class
ABC classNumber of itemsTotal amount required
A20%60%
B20%20%
C60%20%
Total100%100%

Using this distribution of ABC class and change total number of the parts to 14,213.

When equal purchasing policy is applied to all 14,213 components, for example weekly delivery and re-order point (safety stock) of two weeks' supply, the factory will have 16,000 deliveries in four weeks and average inventory will be 2½ weeks' supply.

Application of weighed purchasing condition
Uniform conditionWeighed condition
ItemsConditionsItemsConditions
 All items 14,213 Re-order point=2 weeks' supply
Delivery frequency=weekly
A-class items 200Re-order point=1 week's supply
Delivery frequency=weekly
B-class items 400Re-order point=2 weeks' supply
Delivery frequency=bi-weekly
C-class items 3,400Re-order point=3 weeks' supply
Delivery frequency=every 4 weeks

In comparison, when weighed purchasing policy is applied based on ABC class, for example C class monthly (every four weeks) delivery with re-order point of three weeks' supply, B class bi-weekly delivery with re-order point of 2 weeks' supply, A class weekly delivery with re-order point of 1 week's supply, total number of delivery in 4 weeks will be (A 200×4=800)+(B 400×2=800)+(C 3,400×1=3,400)=5,000 and average inventory will be (A 75%×1.5weeks)+(B 15%x3 weeks)+(C 10%×3.5 weeks)=1.925 weeks' supply.

Comparison of "equal" and "weighed" purchase (4 weeks span)
ABC classNo of items% of total valueEqual purchaseWeighed purchasenote
No of delivery in 4 weeksaverage supply levelNo of delivery in 4 weeksaverage supply level
A20075%8002.5 weeks8001.5 weeksasame delivery frequency, safety stock reduced from 2.5 to 1.5 weeksa, require tighter control with more man-hours.
B40015%16002.5 weeks8003 weeksincreased safety stock level by 20%, delivery frequency reduced to half. Fewer man-hours required.
C340010%13,6002.5 weeks3,4003.5 weeksincreased safety stock from 2.5 to 3.5 weeks' supply, delivery frequency is one quarter. Drastically reduced man-hour requirement.
Total4,000100%16,0002.5 weeks5,0001.925 weeksaverage inventory value reduced by 23%, delivery frequency reduced by 69%. Overall reduction of man-hour requirement.

a) A class item can be applied much tighter control like JIT daily delivery. If daily delivery with one day stock is applied, delivery frequency will be 4,000 and average inventory level of A class item will be 1.5 days' supply and total inventory level will be 1.025 weeks' supply, a reduction of inventory by 59%. Total delivery frequency is also reduced to half from 16,000 to 8,200.

By applying weighed control based on ABC classification, required man-hours and inventory level are drastically reduced.

The ABC concept is based on Pareto's law. [10] If too much inventory is kept, the ABC analysis can be performed on a sample. After obtaining the random sample, the following steps are carried out for the ABC analysis.

Benefits

Selective Inventory Control better known as ABC analysis has great advantages to businesses and among the benefits of this inventory management tool includes:

See also

Related Research Articles

<span class="mw-page-title-main">Pareto principle</span> Statistical principle about ratio of effects to causes

The Pareto principle states that for many outcomes, roughly 80% of consequences come from 20% of causes.

<span class="mw-page-title-main">Cost accounting</span> Procedures to optimize practices in cost efficient ways

Cost accounting is defined by the Institute of Management Accountants as "a systematic set of procedures for recording and reporting measurements of the cost of manufacturing goods and performing services in the aggregate and in detail. It includes methods for recognizing, allocating, aggregating and reporting such costs and comparing them with standard costs". Often considered a subset of managerial accounting, its end goal is to advise the management on how to optimize business practices and processes based on cost efficiency and capability. Cost accounting provides the detailed cost information that management needs to control current operations and plan for the future.

Material requirements planning (MRP) is a production planning, scheduling, and inventory control system used to manage manufacturing processes. Most MRP systems are software-based, but it is possible to conduct MRP by hand as well.

<span class="mw-page-title-main">Inventory</span> Goods held for resale

Inventory or stock refers to the goods and materials that a business holds for the ultimate goal of resale, production or utilisation.

Vendor-managed inventory (VMI) is an inventory management practice in which a supplier of goods, usually the manufacturer, is responsible for optimizing the inventory held by a distributor.

A cycle count is a perpetual inventory auditing procedure, where you follow a regularly repeated sequence of checks on a subset of inventory. Cycle counts contrast with traditional physical inventory in that a traditional physical inventory ceases operations at a facility while all items are counted. Cycle counts are less disruptive to daily operations, provide an ongoing measure of inventory accuracy and procedure execution, and can be tailored to focus on items with higher value, higher movement volume, or that are critical to business processes. Although some say that cycle counting should only be performed in facilities with a high degree of inventory accuracy, cycle counting is a means of achieving and sustaining high degrees of accuracy. Cycle counting can be used to identify root causes of problems in control processes and then monitor the effectiveness of the actions to eliminate the root causes. In contrast, identifying root causes of inventory errors, agreeing on actions to eliminate them to the point of perfecting control processes is virtually impossible with traditional inventory audit approaches.

<span class="mw-page-title-main">Cross-docking</span> Practice in logistics of unloading directly to customer or other transportation

Cross-docking is a logistical practice of Just-In-Time Scheduling where materials are delivered directly from a manufacturer or a mode of transportation to a customer or another mode of transportation. Cross-docking often aims to minimize overheads related to storing goods between shipments or while awaiting a customer's order. This may be done to change the type of conveyance, to sort material intended for different destinations, or to combine material from different origins into transport vehicles with the same or similar destinations.

Economic order quantity (EOQ), also known as financial purchase quantity or economic buying quantity, is the order quantity that minimizes the total holding costs and ordering costs in inventory management. It is one of the oldest classical production scheduling models. The model was developed by Ford W. Harris in 1913, but the consultant R. H. Wilson applied it extensively, and he and K. Andler are given credit for their in-depth analysis.

The beer distribution game is an educational game that is used to experience typical coordination problems of a supply chain process. It reflects a role-play simulation where several participants play with each other. The game represents a supply chain with a non-coordinated process where problems arise due to lack of information sharing. This game outlines the importance of information sharing, supply chain management and collaboration throughout a supply chain process. Due to lack of information, suppliers, manufacturers, sales people and customers often have an incomplete understanding of what the real demand of an order is. The most interesting part of the game is that each group has no control over another part of the supply chain. Therefore, each group has only significant control over their own part of the supply chain. Each group can highly influence the entire supply chain by ordering too much or too little which can lead to a bullwhip effect. Therefore, the order taking of a group also highly depends on decisions of the other groups.

<span class="mw-page-title-main">Operations management</span> In business operations, controlling the process of production of goods

Operations management is concerned with designing and controlling the production of goods and services, ensuring that businesses are efficient in using resources to meet customer requirements.

A lead time is the latency between the initiation and completion of a process. For example, the lead time between the placement of an order and delivery of new cars by a given manufacturer might be between 2 weeks and 6 months, depending on various particularities. One business dictionary defines "manufacturing lead time" as the total time required to manufacture an item, including order preparation time, queue time, setup time, run time, move time, inspection time, and put-away time. For make-to-order products, it is the time between release of an order and the production and shipment that fulfill that order. For make-to-stock products, it is the time taken from the release of an order to production and receipt into finished goods inventory.

Service level measures the performance of a system, service or supply. Certain goals are defined and the service level gives the percentage to which those goals should be achieved.

Safety stock is a term used by logisticians to describe a level of extra stock that is maintained to mitigate risk of stockouts caused by uncertainties in supply and demand. Adequate safety stock levels permit business operations to proceed according to their plans. Safety stock is held when uncertainty exists in demand, supply, or manufacturing yield, and serves as an insurance against stockouts.

<span class="mw-page-title-main">Pareto chart</span> Type of chart

A Pareto chart is a type of chart that contains both bars and a line graph, where individual values are represented in descending order by bars, and the cumulative total is represented by the line. The chart is named for the Pareto principle, which, in turn, derives its name from Vilfredo Pareto, a noted Italian economist.

Field inventory management, commonly known as inventory management, is the task of understanding the stock mix of a company and the handling of the different demands placed on that stock. The demands are influenced by both external and internal factors and are balanced by the creation of purchase order requests to keep supplies at a reasonable or prescribed level. Inventory management is important for every other business enterprise.

The reorder point (ROP), also reorder level (ROL) or "optimal re-order level", is the level of inventory which triggers an action to replenish that particular inventory. It is a minimum amount of an item which a firm holds in stock, such that, when stock falls to this amount, the item must be reordered. It is normally calculated as the forecast usage during the replenishment lead time plus safety stock. In the EOQ model, it was assumed that there is no time lag between ordering and receipt of materials.

In marketing, carrying cost, carrying cost of inventory or holding cost refers to the total cost of holding inventory. This includes warehousing costs such as rent, utilities and salaries, financial costs such as opportunity cost, and inventory costs related to perishability, shrinkage, and insurance. Carrying cost also includes the opportunity cost of reduced responsiveness to customers' changing requirements, slowed introduction of improved items, and the inventory's value and direct expenses, since that money could be used for other purposes. When there are no transaction costs for shipment, carrying costs are minimized when no excess inventory is held at all, as in a just-in-time production system.

A spare part, spare, service part, repair part, or replacement part, is an interchangeable part that is kept in an inventory and used for the repair or refurbishment of defective equipment/units. Spare parts are an important feature of logistics engineering and supply chain management, often comprising dedicated spare parts management systems.

Tool management is needed in metalworking so that the information regarding the tools on hand can be uniformly organized and integrated. The information is stored in a database and is registered and applied using tool management. Tool data management consists of specific data fields, graphics and parameters that are essential in production, as opposed to managing general production equipment.

In inventory management, Economic Batch Quantity (EBQ), also known as Optimum Batch Quantity (OBQ) is a measure used to determine the quantity of units that can be produced at the minimum average costs in a given batch or product run. EBQ is basically a refinement of the economic order quantity (EOQ) model to take into account circumstances in which the goods are produced in batches. The goal of calculating EBQ is that the product is produced in the required quantity and required quality at the lowest cost.

References

  1. Thomas E. Vollmann, Manufacturing planning and control systems for supply chain management
  2. Lun, Lai, Cheng (2010) Shipping and Logistics Management, p. 158
  3. Wong, C., Using ABC Analysis for Inventory Control, APICS Redwood Empire Chapter, last updated on 10 February 2006, archived on 26 August 2009, accessed on 14 July 2024
  4. Purchasing and Supply Chain Management By Kenneth Lysons, Brian Farrington
  5. Wild, T., Best Practice in Inventory Management, (2nd Ed., p. 40)
  6. Ultsch, Alfred, Jörn Lötsch. "Computed ABC analysis for rational selection of most informative variables in multivariate data." PLOS One 10.6 (2015): e0129767.
  7. Kringel, D., Ultsch, A., Zimmermann, M., Jansen, J. P., Ilias, W., Freynhagen, R., ... & Resch, E. (2016). Emergent biomarker derived from next-generation sequencing to identify pain patients requiring uncommonly high opioid doses. The pharmacogenomics journal.
  8. Iovanella, A.: Vital few e trivial many, Il Punto, pp 10-13, July, 2017.
  9. Barbara Pawelek, Jozef Pociecha, Mateusz Baryla, ABC Anal-ysis in Corporate Bankruptcy Prediction, Abstracts of the IFCS Conference, p 17, Tokyo, Japan,2017
  10. Pareto's law in this example is that a few high usage value items constitute a major part of the capital invested in inventories whereas a large number of items having low usage value constitute an insignificant part of the capital.
  11. Production Management: Latest Edition. SBPD Publications. 2016-12-14. ISBN   978-93-83697-83-0.
  12. "Effective Techniques for Inventory Stock Control - SIPMM Publications". publication.sipmm.edu.sg. 2018-10-14. Retrieved 2023-03-24.