GUIDE is an accelerated cohort survey with nationally representative samples of infants, school-age children, and their parents. The samples will be surveyed at regular intervals using harmonized questionnaires, until the children are 24-years old. The two cohorts (birth and 8-year-old cohort) will take place in parallel, making possible comparisons early in the life of the survey, hence more responsive to policy cycles. Major domains and measurement targets are the Macrosystem (Economy, Agriculture, Housing, Health, Education, Legal, Environment, Family supports) Proximal developmental contexts: Environmental (Home, School, Leisure Neighbourhood, Services, Cultural facilities, Digital); Social (Parents, Teachers, Friends); Experiences (Nutrition, Nurturing, Wealth, Safety / bullying, Inclusivity, Equality, Voice promoting, Rights, Caring / valuing); Functioning (Physical, Cognitive, Emotional, Behavioural, Social); Wellbeing- Hedonia (Positive affect, Negative affect, Life satisfaction, Safety) and Eudaimonia (Meaning, Purpose, Autonomy, Competence, Relatedness, Self-acceptance, Voice). By considering the multiple dimensions of child wellbeing, policymakers will gain insights into the various aspects of children's lives that require attention. This approach goes beyond traditional economic indicators and considers both material and non-material factors that influence children's overall wellbeing and development. The goal is to provide policymakers and stakeholders with a holistic understanding of the conditions and opportunities that affect children's lives. The GUIDE data will be used by a broad community including health, child development, family studies, psychology, sociology, demography, and economics and will generate cross-culturally comparative results of great value to education, child and youth services, and government. At a national level, GUIDE will support the design of evidence-based policies. At an international level, data from GUIDE will provide a unique insight into factors contributing to successful policies through rigorous comparisons between European countries. GUIDE has developed through a series of projects worth €11,876,479, funded by the European Commission: MYWeB (GA 613368), the European Cohort Development Project (GA 777449), COORDINATE (GA 101008589) and GUIDEPREP (GA 101078945). GUIDE was appointed to the European Strategy Forum on Research Infrastructures (ESFRI) 2021 Roadmap and has received political and financial support commitments from several EU countries. To guarantee long-term sustainability of the GUIDE research infrastructure we are establishing appropriate links with government and research organisations, third sector organisations, and stakeholders involved in national and European policy development networks and funding bodies. GUIDE has political support, by way of formal letters from government ministries, from ten countries (Croatia, Estonia, Hungary, Ireland, Latvia, Portugal, Slovakia, Slovenia, Spain, and UK). Currently, the teams at GUIDE are in ongoing discussions with five new countries who are in support of the project and show keen interest in joining the consortium. Those countries include Denmark, Iceland, Lithuania, Poland, and Sweden. All GUIDE partners continue to actively seek national funding. A Political Support Committee is under development and will include key individuals across Europe to help secure the future of GUIDE.

The GUIDE European data will be open access and thus will be used by a broad community including health, child development, family studies, psychology, sociology, demography, and economics. The data will generate cross-culturally comparative results of great value to education, child and youth services, and government. At a national level, GUIDE will support the design of evidence-based policies. At an international level, data from GUIDE will provide a unique insight into factors contributing to successful policies through rigorous comparisons between European countries. There is currently no single data source to support the comparative analysis of the wellbeing of children and young people across Europe as they grow up. Some European countries have regularly invested in cohort surveys and have benefited from analyses drawn from longitudinal studies, such as Growing Up in Ireland, the British Cohort Studies, the French Longitudinal Study of Children, the Danish Longitudinal Survey of Children, and the National Education Panel on Early Education and Schooling in Germany. The merits of collecting national longitudinal data are widely recognised, and yet the current studies are not easily comparable as they contain different questions and are conducted at different times and on different age groups.