In this study, we leverage state policy variation and the random assignment design of the HSIS to address the following research questions: (1) Are state policy characteristics associated with variation in children's likelihood to enroll in formal and high quality ECE within the control group? (2) Are state policy characteristics similarly associated with variation in children's likelihood to enroll in formal and high quality ECE within the Head Start group? (3) Are state policy characteristics similarly associated with variation in Head Start impacts on children's enrollment in formal ECE and high quality ECE? (4) Which state policy characteristics are most strongly related to children's enrollment in formal and high quality ECE and to Head Start's impact on this behavior? (author abstract)