Child poverty and under-5 children services spending on early childhood development in England: A longitudinal local area ecological study of children born between 2017 and 2023

OBJECTIVES: To investigate the contribution of area-level differences and changes over time in child poverty, and under-5 children's services spending, to trends in children not developmentally on track at 2-2.5 years. STUDY DESIGN: Longitudinal, area-level study, of children born between 2016/17 to 2022/23 in England (538 observations, 119 upper-tier local authorities). METHODS: Children not on track in Any Domain, and in specific domains, were assessed using the Ages and Stages Questionnaire 3 (ASQ-3), expressed as a rate per 100 children. Using within-between models controlling for confounders, we estimated associations between relative child poverty rates (