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