BullwhipSim
Experience the Bullwhip Effect firsthand. Play as a Retailer in a 4-tier supply chain and discover how small demand changes create massive upstream volatility.
Based on the MIT Beer Distribution Game — Sterman (1989), Lee, Padmanabhan & Whang (1997)
20 Rounds
~30–45 min
Single Player
AI opponents
4 Tiers
Supply chain
Academic
Debrief included
Supply Chain Structure
Information and material flows — orders travel upstream (right), shipments travel downstream (left)
Supply Chain Roles
Each tier only sees orders from the tier immediately downstream — never actual customer demand.
Retailer
Tier 1
Faces actual customer demand directly. Must balance holding costs against stockout risk. Your ordering decisions are the primary focus of this simulation.
Responsibilities
- Observe weekly customer demand
- Check current inventory & backlog
- Review pipeline (units in transit)
- Decide order quantity to Wholesaler
💡 Your orders are the starting point of the Bullwhip Effect. Small overreactions here cascade dramatically upstream.
Start Inventory
12
Pipeline
4+4
Wholesaler
Tier 2
Receives orders from the Retailer. Has no visibility into actual customer demand — only sees Retailer's orders. AI uses a demand-signal-plus-safety-stock heuristic.
Responsibilities
- Receives Retailer orders as its "demand"
- Cannot see actual customer demand
- Adds safety stock based on perceived risk
- Orders from Distributor with amplification
💡 Wholesaler sees Retailer orders, not customer demand. Any amplification you create here doubles upstream.
Start Inventory
12
Pipeline
4+4
Distributor
Tier 3
Two tiers removed from customer demand. Receives only Wholesaler orders. The information distortion at this level is typically 3–5× actual demand variance.
Responsibilities
- Receives Wholesaler orders as its "demand"
- No visibility into Retailer or customer
- Amplifies orders further upstream
- Orders from Factory
💡 At this distance from real demand, AI ordering is heavily influenced by backlog panic and safety stock accumulation.
Start Inventory
12
Pipeline
4+4
Factory
Tier 4
The most upstream node. Sees only Distributor orders, which by this point may be 5–10× actual customer demand. Produces to order with a production lead time.
Responsibilities
- Receives Distributor orders as its "demand"
- Must produce (cannot simply reorder)
- Highest demand variance of all tiers
- Experiences the worst cost consequences
💡 Factory is the final amplifier. In real supply chains, factory production swings are often catastrophic — idle capacity followed by overtime.
Start Inventory
12
Pipeline
4+4
Game Mechanics & Rules
How each round works — read carefully before starting
Cost Structure
Holding Cost
₹0.50
per unit per week in inventory
Backlog Cost
₹1.00
per unit per week unfulfilled
Each Round (Week) — In Order
- 1📦 Receive shipment from pipeline (units ordered 2 weeks ago arrive)
- 2👁️ Observe incoming customer demand for this week
- 3🚚 Ship what you can from inventory; remainder becomes backlog
- 4💰 Calculate holding cost (inventory × ₹0.50) + backlog cost (backlog × ₹1.00)
- 5✍️ Decide your order quantity and submit to Wholesaler
- 6🤖 AI tiers (Wholesaler, Distributor, Factory) process their turns simultaneously
The 2-Week Pipeline Delay
Orders placed today arrive in 2 weeks. This delay is the root cause of the Bullwhip Effect — you cannot see what is already in transit, so you tend to order more than needed, causing inventory to overshoot when the pipeline arrives.
Scoring
The Bullwhip Effect — Academic Primer
Lee, Padmanabhan & Whang (1997) · MIT Sloan Management Review
Core Concept
The Bullwhip Effect describes the phenomenon where small fluctuations in consumer demand cause progressively larger fluctuations in orders placed by each upstream supply chain tier — like the tip of a whip amplifying a small wrist flick into a massive crack.
Four Root Causes (Lee et al., 1997)
Demand Signal Processing
Each tier uses observed orders (not real demand) to forecast. They add safety stock, creating order inflation at every link.
Rationing & Shortage Gaming
When supply is scarce, buyers order more than needed to secure allocation — inflating apparent demand further.
Order Batching
Ordering in large periodic batches (e.g. weekly) rather than continuously introduces artificial demand spikes.
Price Fluctuations
Promotions and discounts cause forward buying — buyers stock up beyond current needs, distorting the demand signal.
Variance Amplification Ratio
A ratio > 1 indicates Bullwhip Effect. Typical real-world values:
Retailer: 1.2–2× · Wholesaler: 2–4× · Distributor: 4–8× · Factory: 8–15×
Real-World Examples in India
Start Simulation
No login required — your results are shown at the end of the session