“…Essig (2011) states that "it makes sense not to talk about 'the' purchasing strategy; instead strategic sourcing decisions […] are always decided specifically for each category and their supply market conditions" (p. 143). In other words, purchasing may develop specific strategies for homogenous supply markets or families of purchased products and services (Cousins et al, 2008b;Karjalainen andSalmi, 2013), called 'categories' (O'Brien, 2012), 'commodity groups' (Schiele, 2007), 'material groups' (Horn et al, 2013), 'product groups' (Luzzini and Ronchi, 2011) and 'product families' (Monczka et al, 2008). These commodity or category groups are defined as "general categories of purchased items, including materials or services of a similar type provided by the same group of suppliers" (Schiele et al, 2011a), which constitute "a single supply market" (Schiele, 2007, p. 279).…”