Illinois Longitudinal Data System – An Introduction

The Illinois Longitudinal Data System (ILDS) was formed in 2013 as a collaborative body to facilitate the linkage of records across state agencies over time.  The objective was to more efficiently analyze data and program impacts across data systems to improve education, human services, and workforce outcomes.  By linking these records, research involving various data sources across multiple agencies could increase program efficiency and effectiveness.

To oversee record linkage, the ILDS selected Northern Illinois University (NIU) as the Centralized Demographic Dataset Administrator (CDDA) in 2015.  The ILDS pursued a federated model for the data system that allows each agency to maintain its own data and policies regarding use of that data, while allowing the CDDA to use data from the state agencies to match records and maintain a Master Client Index (MCI).  Contained in the MCI are a select number of fields and the CDDA-IDs, which provide the basis for supporting research involving records from across several state agencies.

Progress towards providing the CDDA-IDs for school districts and post-secondary institutions is being made.  As these IDs become more accessible for districts and institutions, there are increasing opportunities to conduct research using data from multiple state agencies.  Additionally, the IDs can support improved data sharing and research at the local level between school districts and postsecondary institutions.  To learn more about the potential of using CDDA-IDs for your district’s or institution’s research interests, please contact William Holderfield of Northern Illinois University’s Center for Governmental Studies at

May 2020