Today's official crime statistics are based solely on the police registers and have several methodic limitations. Other data sources based on survey data do not necessarily form the same picture of the extent and development of child and youth crime as the official crime statistics. There is uncertainty as to how the developments in child and youth crime are actually measured and how the statistics are understood. In order to understand the extent, development and possible explanations of the development in the child and youth crime, a solid data basis is needed. The aim of the assignment is to procure an independent, research-based and comprehensive knowledge basis for the development of child and youth crime in Norway. It includes: 1. Map existing data sources 2. Highlight how developments in child and youth crime can be collated and understood over time 3. Recommend measures for long-term high quality of the knowledge basis The knowledge will form an important basis for authorities and other actors who work with the prevention of child and youth crimes being able to implement as much effort as possible. The final delivery deadline for the contract is 30 November 2027. The assignment has a value of NOK 1.8 million excluding VAT. See annex 1 of the contract for further details on the delivery.