Competition law is rooted in economic theory, and economics provides many of the standard tools often applied in competition investigations. As a result, a strong foundation in economics is an invaluable asset for practitioners in this area of law. This is the third edition of the popular and well-regarded practitioner guide to the economic principles of competition law. Written in accessible language for non-technical readers, it covers first economic principles by applying them directly to competition cases. It covers all major topics in competition law where economics is relevant: the core themes of market definition, market power and dominance, mergers, and anti-competition practice, as well as less familiar but important areas such as state aid, remedy design, damages, and use of experts in competition cases. Topics are introduced by posing compelling questions based on real cases from around the world. This third edition has been updated to include the latest developments in the last five years, including the rise of digital platforms with strong network effects, killer acquisitions in innovative markets, competition concerns in labour markets, and 'green' agreements related to climate change.