Education Commission of the States has researched Statewide Longitudinal Data Systems (SLDS) policies and resources in all states and the District of Columbia to provide this comprehensive resource. Click on the questions below for 50-State Comparisons that show how all states approach specific SLDS policies. View a specific state’s approach by selecting the state profiles page. Defining Statewide Longitudinal Data Systems and Core Agencies: Four state agencies are designated as core agencies within any SLDS: early learning, K-12, postsecondary and workforce. For the purposes of this 50-State Comparison, an SLDS is defined as a data system with formal connections across two or more of these core agencies. States with at least two of these core agencies in their data systems are designated as having established an SLDS. As such, the data systems that meet this definition might not always be those systems associated with the federal SLDS Grant Program. (author abstract)