These studies represent a large and important knowledge base, and they have influenced education policy development globally. The Nordic countries represent a unique "laboratory" for in-depth analyses of the outcomes of these studies because of the many cultural similarities combined with clear national characteristics with respect to results and policy development. The biannual Northern Lights publications aim to present highly policy-relevant analyses in a Nordic context in order to enhance the use and understanding of the data from large-scale assessments, and to stimulate Nordic cooperation.