Supply Chain Management (SCM) 101: Inventory Management Advanced ABC FSN VED Classifications Inventory Analysis Methods

What This Is

Inventory classification methods, such as ABC, FSN, and VED, are essential in supply chain management for optimizing inventory levels, reducing costs, and improving service levels. These methods categorize inventory items based on their value, frequency of usage, or other criteria, enabling companies to focus on high-value or high-usage items and reduce inventory holding costs. For example, Amazon uses ABC analysis to categorize its inventory items, focusing on high-value items such as electronics and low-value items such as packaging materials.

Key Frameworks & Formulas

• ABC Analysis: A method of categorizing inventory items into three groups (A, B, and C) based on their value or usage.
• FSN Classification: A method of categorizing inventory items into four groups (Fast, Slow, Normal) based on their usage frequency.
• VED Classification: A method of categorizing inventory items into three groups (Very Essential, Essential, and Non-Essential) based on their importance and usage.
• EOQ (Economic Order Quantity) Formula: EOQ = √(2DS/H), where D = demand, S = ordering cost, and H = holding cost.
• Safety Stock Formula: Safety Stock = Z × σ × √L, where Z = Z-score, σ = standard deviation, and L = lead time.
• Service Level Formula: Service Level = (1 - α)^n, where α = probability of stockout and n = number of periods.
• Inventory Turnover Ratio: Inventory Turnover Ratio = COGS / Average Inventory, where COGS = cost of goods sold and Average Inventory = average inventory level.
• Days Inventory Outstanding (DIO): DIO = Average Inventory / (COGS / Number of Days), where COGS = cost of goods sold and Number of Days = number of days in the period.

Step-by-Step Application

1. Classify Inventory Items: Use ABC, FSN, or VED classification to categorize inventory items based on their value, usage frequency, or importance.
2. Determine Inventory Levels: Based on the classification, determine the optimal inventory levels for each item, considering factors such as demand, lead time, and holding costs.
3. Calculate Safety Stock: Use the safety stock formula to determine the additional inventory needed to ensure service levels are met.
4. Optimize Inventory Levels: Adjust inventory levels based on the classification and safety stock calculations to minimize costs and maximize service levels.
5. Monitor and Review: Regularly review and update the classification and inventory levels to ensure they remain optimal.

Common Mistakes

• Mistake: Incorrectly classifying inventory items, leading to suboptimal inventory levels.
• Correction: Use a systematic approach to classify inventory items, considering multiple criteria such as value, usage frequency, and importance.
• Mistake: Failing to consider safety stock when determining inventory levels.
• Correction: Use the safety stock formula to determine the additional inventory needed to ensure service levels are met.
• Mistake: Not regularly reviewing and updating inventory levels.
• Correction: Regularly review and update inventory levels to ensure they remain optimal.

Exam / Certification Tips

• Tricky Distinction: Understand the difference between ABC and FSN classification methods.
• Common Question Pattern: Be prepared to calculate safety stock and determine optimal inventory levels.
• Important Formula: Remember the EOQ and safety stock formulas.

Quick Practice Problem

A company has an average inventory level of $100,000 and a cost of goods sold of $500,000. What is the inventory turnover ratio?

Answer: 5 Explanation: Inventory Turnover Ratio = COGS / Average Inventory = $500,000 / $100,000 = 5

Last-Minute Cram Sheet

• ABC Analysis: Categorizes inventory items into three groups (A, B, and C) based on their value or usage.
• FSN Classification: Categorizes inventory items into four groups (Fast, Slow, Normal) based on their usage frequency.
• VED Classification: Categorizes inventory items into three groups (Very Essential, Essential, and Non-Essential) based on their importance and usage.
• EOQ Formula: EOQ = √(2DS/H)
• Safety Stock Formula: Safety Stock = Z × σ × √L
• Service Level Formula: Service Level = (1 - α)^n
• Inventory Turnover Ratio: Inventory Turnover Ratio = COGS / Average Inventory
• Days Inventory Outstanding (DIO): DIO = Average Inventory / (COGS / Number of Days)
• ⚠️ Postponement: Delays final configuration, not production – it's a push-pull boundary strategy.