📈 Forecast-Driven Supply

Safety stock is reactive: you wait for stock to fall to a reorder point, then buy. This is the opposite — proactive replenishment, where a forecast drives supply. You plan orders to match what you expect to sell. Shape the forecast below and watch how well (or badly) supply keeps up.

Forecast

Each step of the chart is one of these
The baseline the forecast is built on
% of the average added each period (can be negative)
Peak rises this % above the average (and dips the same below)
Periods in one full up-and-down cycle

Supply & reality

Periods between planning an order and its arrival
On: order now for demand a lead time from now. Off: order to today's forecast — so supply arrives late.
How far actual demand randomly strays from the forecast — measure it with Forecast Accuracy (MAPE & bias)
Buffer that absorbs forecast error
On-hand inventory Forecast (drives supply) Actual demand Safety stock Stockout
Period
0
Forecast now
–
On-hand
–
Service level (achieved)
–
Stockout periods
0
Avg. on-hand
–

What you're seeing

Every period, the forecast (dashed line) says how much you expect to sell. Supply is planned to meet it — so the forecast, not a reorder point, is what pulls in stock. Then actual demand (gold bars) arrives and eats the inventory. When the forecast is good and you plan ahead, on-hand hugs the safety-stock buffer. When it isn't, gaps open up.

Forecast(t) = average + trend + seasonal =  –

Try this: pick Linear trend and turn “Plan ahead for lead time” off — supply is always ordering to yesterday's smaller forecast, so it falls permanently behind a growing market. Turn it back on and the gap closes. Then switch to Seasonal: with planning off, every delivery arrives a lead time late, so you run dry on the way up to each peak and drown in stock on the way down. This lag is the signature failure of forecast-driven systems — and why planners forecast the lead-time-ahead demand, not today's.