Worst Practices Supply Chain Planning: Equal-Split Weekly Disaggregation That Erases Real Demand Patterns

📉 Equal-split forecasts in SAP IBP: convenient, but is it costing you? 🤔

A pattern I see often in IBP implementations: the monthly forecast gets disaggregated to weeks using an equal split.

400 units in the month?

That becomes 100 / 100 / 100 / 100 across the four weeks. Clean. Simple. ✨

And in the example below, it lets the open forecast key figure calculate neatly against actual sales orders. However weekly demand rarely has a uniform pattern – if it does then you are lucky. It has a pattern of its own.

If you did not design your SAP IBP the right away, then you have to use complex consumption rules to take care of actual weekly demand patterns (and of course fret over in the S&OE meetings).

✅ Why teams default to equal split:

⚡ Fast to configure, easy to explain to the business
🧮 Keeps monthly totals intact, so S&OP numbers reconcile cleanly
📈 Works reasonably well for products with stable, non-seasonal weekly demand
🔄 Simplifies forecast consumption logic when sales orders arrive lumpy

⚠️ Where it quietly hurts you:

🎢 Real demand is rarely flat — promotions, paydays, month-end pushes, and customer ordering patterns create weekly shape that an equal split erases
🏭 Supply plans inherit that flat signal, which can mistime production, inventory builds, and deployment
🎯 Forecast accuracy at the weekly level looks worse
🙈 It hides the conversation the demand planner should be having: “what does this month actually look like week by week?”

There are a few best practices available to design the right weekly forecast or optimally disaggregate the monthly forecast into weekly buckets.

Equal split isn’t wrong. It’s just a default that should be a deliberate choice, not an unexamined one. 🎯

Equal split isn’t wrong — but it should be a deliberate design choice, not an unexamined default. Explore our SAP IBP Usability Consulting or Contact Us for a disaggregation design review.