A data structure programmatically links the first product to a second product. The second product is historically purchased by the customer whenever the customer has also purchased the first product. A determination is made as to whether the customer purchased the second product together with the first product based upon the sales data. When the customer has failed to purchase the second product with the first product, instructions are transmitted to the retail store over the network to perform a verification that the second product is out-of-stock. An outcome of the verification from the retail store is received via the network. A determination is made as to a level of certainty that the second product is actually out-of-stock based upon an analysis of the sales data and the outcome of the verification. When the level of certainty exceeds a predetermined threshold, the PI value is adjusted to zero.