VED

401. VED

401.1. VED Analysis (Vital / Essential / Desirable)

Classify items by criticality of stockout. Independent of value or variability — it’s about consequence-of-failure.

401.1.1. The criticality split

V items (Vital): stockout halts operations or risks safety / regulatory compliance. No tolerance for unavailability.
E items (Essential): stockout causes significant disruption but operations can continue (degraded performance, workarounds available).
D items (Desirable): stockout is an inconvenience; operations continue normally with minor impact.

401.1.2. Why classify by criticality

ABC, XYZ, and FSN look at value, variability, and frequency. None of these capture what happens if you run out. A $1 fuse in a hospital ventilator is Vital even though it’s low-value, low-variability, and slow-moving.

Criticality is what justifies:

Higher service levels (target 99.9% for V vs 95% for D)
Larger safety stocks regardless of holding cost
Multiple suppliers for V items (sourcing redundancy)
Emergency procurement contracts for V items

VED is most prevalent in:

Healthcare (drugs, surgical supplies, life-support spares)
Manufacturing maintenance (MRO spares — a $50 bearing that holds together a $500K production line)
Aviation / military (anywhere a single failure has outsized cost)
Utilities (grid, water, telecom — single-point-of-failure components)

401.1.3. Procedure

For each SKU, ask: what’s the cost of a stockout?
Categorize:
- V: stockout = life, safety, large operational halt, or regulatory violation
- E: stockout = significant downtime / customer impact, but workarounds exist
- D: stockout = minor inconvenience
Apply differential service levels and stocking policies.

401.1.4. Service-level targets by class

Class	Target CSL	Stocking philosophy
V	99.5–99.99%	Never stockout. Multiple suppliers, emergency stock, expedited freight contracts. Safety stock dominates regardless of holding cost.
E	95–99%	Standard high service. Single reliable supplier; safety stock per (Q, r) or (s, S) policies.
D	85–95%	Cost-optimized. Accept occasional stockouts to keep holding costs in check.

401.1.5. VED + ABC = a richer matrix

VED is often combined with ABC into a 3×3 grid (similar to ABC-XYZ):

AV: high-value, vital — heavy investment in inventory and supplier diversification.
CV: low-value, vital — overstock liberally; the holding cost is trivial against the stockout cost.
AD: high-value, desirable — most attention to lean inventory, can afford some stockouts.
CD: low-value, desirable — minimum effort; overstock or eliminate.

The asymmetric cells — low-value vital especially — are why VED matters: ABC alone says “spend little time on it”; VED says “but never run out.”

Example

Given: maintenance spares for a small manufacturing line.

Item	Unit cost	Annual demand	Stockout consequence
Critical PLC controller	$2,000	2 / year	Production line halts; $50K/day lost output
Standard motor bearing	$50	12 / year	Specific machine offline; workaround possible
Lubricant pail	$80	40 / year	Maintenance delayed a few hours
Spare bolt set	$5	200 / year	Small inconvenience; alternative bolts on hand
Calibration weight	$300	1 / year	Required for monthly calibration; no substitute; can pause operations until next cal cycle

Step 1 — assign VED

Item	Class	Reasoning
Critical PLC controller	V	Halts whole line; $50K/day downtime cost
Standard motor bearing	E	One machine offline; workarounds available
Lubricant pail	D	Maintenance delay only; common item
Spare bolt set	D	Substitutes available
Calibration weight	V	Compliance requirement; no substitute

Step 2 — set service levels

Item	VED	CSL target	Implied $𝑧$
Critical PLC controller	V	99.9%	3.09
Standard motor bearing	E	97%	1.88
Lubricant pail	D	90%	1.28
Spare bolt set	D	90%	1.28
Calibration weight	V	99.5%	2.58

Step 3 — compare safety stocks

Suppose the standard motor bearing had monthly demand $𝜎$ = 0.5 units, lead time $𝐿$ = 1 month. Safety stock at:

95% (default): $𝑧 = 1.65$ → SS = 0.83 units → round up to 1.
97% (E-target): $𝑧 = 1.88$ → SS = 0.94 → round up to 1.
99.9% (if it were V): $𝑧 = 3.09$ → SS = 1.55 → round up to 2.

Even at the highest service level, total SS for a slow-moving item is just 2 units. The cost difference is one extra bearing in stock — $50 — vs the downtime cost if you stock out. Trivially worth it for E or V class items.

Step 4 — interpret cross-classification with ABC

Critical PLC controller: A-class ($4K annual value), V-class. AV — biggest priority. Multiple suppliers, expedited shipping contract, generous safety stock.
Calibration weight: C-class ($300/year), V-class. CV — low value, vital. The right answer here is overstock without thinking. Holding cost is negligible; consequences of stockout are large. Carry 2 units instead of 1.
Spare bolt set: C-class, D-class. CD — automated two-bin replenishment. Don’t waste planning effort.

The asymmetric cell — CV (low value vital) — is the most common surprise in VED analysis. Operations teams often under-stock low-value vital items because ABC says “C-class, don’t bother”. VED corrects this.