For academics, regulators and policymaker alike, it is crucial to measure financial sector competition by means of reliable, well-established methods. However, this is easier said than done. The goal of this Handbook is to provide a collection of state-of-the-art chapters to address this issue. The book consists of four parts, the first of which discusses the characteristics of various measures of financial sector competition. The second part includes several empirical studies on the level of, and trends in, competition across countries. The third part deals with the spillovers of market power to other sectors and the economy as a whole. Finally, the fourth part considers competition in banking submarkets and subsectors.