This project has three overarching goals. The first is to provide a longitudinal, national, examination of ECEC supply, focusing both on childcare provider organizations and on childcare workers. A primary advantage of our approach over previous work is our ability to merge national, longitudinal datasets—several of which are newly-available and highly restricted—to provide a far more comprehensive understanding of the supply in this sector than has been possible in previous research. The second aim of this study is to explore the extent to which regulations that specify quality thresholds for family daycare homes, childcare centers and preschools impact supply in the industry. Unlike other studies which have limited their analysis to a single ECEC subsector (i.e. childcare centers) our study will explore the impact of regulations across all types of ECEC programs including family daycare homes and state preschools. The third goal is to examine the link between ECEC supply and child outcomes. To do this we combine our supply-side data with data from three large nationally representative datasets on children. Using these datasets, we explore how the school readiness (i.e. pre-literacy and pre-mathematics competency, social skills, etc.) of young children is associated with the availability of childcare opportunities in their communities.