Abstract
This study creates a framework for evaluating the sales impact of adding an online channel to an existing network of physical stores. Using a unique database consisting of pooled customer data from a Swedish retailer's online and offline stores, it investigates the purchase behavior of customers before and after the introduction of an online channel. The data overcome a crucial obstacle present in previous studies in that they permit matching of individual-level customer data for both online and offline behavior. The results show significant and substantial effects of online channel introduction on customer acquisition as well as on cannibalization of physical stores.