The document discusses market power and efficiency in various contexts. It begins by defining market share and how it differs from market power. It then provides data on market shares in the UK retail banking sector in 2010. It discusses how market power can be self-reinforcing for industry leaders through economies of scale, profits to reinvest, and habitual consumption. The document also defines different types of economic efficiency and how monopoly pricing can lead to allocative inefficiency and deadweight loss compared to perfect competition. Finally, it applies concepts of economies of scale, both internal and external, to analyze falling prices in the smartphone industry.