Based on the work of Stock (1992) and Kopicki et al. (1993), Carter and Ellram (1998) conceptualized the idea of a RL hierarchy. This hierarchy posits that RL activities that require the least amount of resources in order to extract the greatest amount of value should be pursued first. Others (Prahinski and Kocabasoglu, 2006; Rogers et al., 2002; Staikos and Rahimifard, 2007) have since refined the RL hierarchy. In order from most desirable to least desirable, these RL activities are: