Abstract: A method is provided that comprises determining a first time period during which a first product is available in an inventory at a point of purchase according to a model that uses (a) sales data, (b) inventory data, or (c) both sales data and inventory data. The inventory data comprises data from an inventory management system, sampled during the first time period, as an input. The method further comprises determining a second time period during which the first product is unavailable in the inventory according to the model and comparing a first time period sales data to a second time period sales data to determine a product unavailability effect. The method also comprises using the product unavailability effect to change an assortment at the point of purchase.