The study builds on previous industry initiatives by the World Federation of Advertisers and the Association of National Advertisers in the United States. It sets out to identify each element of the supply chain, understand the services delivered and the costs applied at each stage, and provide a transparent picture by mapping supply chains from start to finish, using real market data. The intention was to provide a more transparent view of the UK programmatic supply chain, for the benefit of all participants and the industry as a whole. The study reveals the depth of the supply chain’s complexity. 1000+ distinct supply chains were identified; across the 15 advertisers, experts and data scientists were able to end-to-end match 290 chains (31m impressions) all the way to the 12 publishers.