Why probability densities beat averages for reorder points
Most ERP systems plan with averages. That sounds reasonable – and is exactly why safety stocks are too high.
Planning with the average means planning for a case that almost never occurs. Actual demand for an item fluctuates – sometimes strongly, sometimes weakly, often asymmetrically. An average compresses all of that information into a single number and throws away exactly what matters most for replenishment: the risk.
Traditional systems compensate with blanket safety stocks. The result: well-behaved items sit on too much inventory, sporadic items on too little. A probability density, by contrast, describes how likely every possible demand quantity is. From it, the reorder point can be derived directly from the desired service level – individually per item, instead of one buffer for all.
In our projects, precisely this step – from point forecast to distribution – is the biggest lever: 15–30% less inventory at the same or better availability. Not because the model knows the future better, but because it is honest about its own uncertainty.