The entire UK economy relies on some form of intellectual property (IP), because virtually every industry either produces or uses it. The flipside of the value of IP is the harm caused by IP theft, involving creating and selling counterfeit and pirated products. Information on the magnitude, scope and trends of counterfeit and pirated trade is critical to understand the nature of the problem and how the situation is evolving. It is also essential for designing and implementing effective policies and measures to combat illicit operations. This report describes an analysis conducted by the OECD of the economic impact on the UK economy of the global trade in counterfeit and pirated goods. This chapter takes a step-bystep approach to explain the unique methodology used for the analysis.