A product assortment planning system determines scaled performance metric values for an assortment of products. The system includes a data store storing performance metric values for an assortment of products including a target assortment of products and a source assortment of products, an equivalization unit and a scaling unit. The equivalization unit equivalizes the performance metric values for the source assortment of products. The scaling unit determines incrementality assumptions. The incrementality assumptions are an estimation of an amount of cannibalization that occurs for the target assortment of products as a result of combining the source assortment of products with the target assortment of products. Scaled performance metric values are calculated for each product in the assortment of products based on the equivalized performance metric values and the incrementality assumptions.