Definition
The grouping mechanism that combines multiple material numbers into one predictive unit is the particle size of the PSI table.
In detail
A PSI Key is a grouping mechanism that combines multiple part numbers into one forecasting unit, serving as the row granularity of the PSI (Production, Sales, Inventory) table. It addresses granularity issues in forecasting and inventory management: forecasting by individual part numbers results in high volume and volatility, making it difficult to manage; grouping by product family or customer segment provides more stability and manageability. Unlike SKUs (part numbers), a PSI Key is a management unit that can include multiple part numbers, used to aggregate demand and plan uniformly. Outputs typically include a row in the PSI table containing forecast, actual, and inventory data.
Example in practice
A manufacturing company had thousands of SKUs. Forecasting each individually was labor-intensive and inaccurate. They grouped SKUs into about 50 PSI Keys by product family and customer group. Each month, they balanced production, sales, and inventory on the PSI table by Key, then decomposed to specific part numbers. This ensured forecast stability and facilitated cross-departmental communication, ultimately forming a clear supply plan.