One of the significant developments associated with the increased globalization of economic activity since the 1970s has been the rise of city-regions as a key scale of economic management. One model that has been used to understand this trend is the 'global city' model - first popularized by Saskia Sassen & later by Peter Taylor. This model contends that cities serve as key nodes for international exchange due to their concentration of advanced producer services. According to Rutland and O'Hagan (2007), what kind of knowledge do these services rely on, and what is needed for the exchange of this knowledge? According to the Pain (2008) reading and class discussion, which kind of advanced producer service is most important for the 'global city'? One challenge that the rise of city-regions present is a tension between their economic functions and their political power. Most city-regions have informal, rather than formal, governance models. According to Harrison (2008) reading, what are key features that characterize the formal 'city-region' governance model?