This chartbook presents nationally representative estimates of all Workers in Center-based Early Care and Education (ECE) classrooms educating children age 5 years and under, not yet in kindergarten. Using data from the 2012 and 2019 National Survey of Early Care and Education (NSECE), the chartbook describes counts and percentages of workers, workers’ individual characteristics, and information about the context in which they worked. The chartbook also identifies statistically significant changes in the distribution of these characteristics among the workforce in center-based classrooms between 2012 and 2019. (author abstract)