This figure depicts center-based ECE program QRIS participation numbers by program density (i.e., the percent of eligible programs that are participating) and QRIS years of operation. Each circle represents a different state where a larger circle corresponds to higher program participation rates. Thirty six QRIS reported numbers for both density and participation. QRIS that have been in operation for between six to twelve years tend to have varying levels of density but uniformly low participation rates. The QRIS are in small (e.g., Vermont, Delaware) to mid-sized states (e.g., Minnesota, South Carolina). States with the highest participation numbers tend to have a QRIS that has been in operation less than six years or more than twelve years. A few states (i.e., Illinois, New Hampshire, Oklahoma) require QRIS participation for center-based ECE programs and therefore report densities of 100%.