Managers at e-commerce firms are in need of proven methods for ongoing website evaluation. However, current approaches to website evaluation are not perfectly suited to the task at hand. This paper proposes a new business value-driven approach to website evaluation, which is theoretically grounded in the economic theory of production. We view online shopping as an economic production process in which customers are using various functionalities of an e-commerce website in order to complete a purchase transaction. This view enables us to formulate a novel perspective on website performance — the ability to transform inputs (i.e., use of website functionalities) into outputs (i.e., completed purchase transactions). We propose two DEA-based metrics, InefficiencyBreadth and UnitInefficiency that help identify website functionalities that are potentially ineffective.