Project Summary/Abstract The proposed research will provide a methodological framework for investigating the impact of policy (i.e., lag- time, mechanism, and equity) on population health while contributing to the evaluation of the Affordable Care Act (ACA) by assessing the impact of the ACA on one aspect of reproductive health, unintended pregnancy. The first specific aim of the project is to assess the impact of the ACA on unintended pregnancy. Within this aim, I will a) estimate the effect of the ACA on unintended pregnancy, and determine the lag period that precedes this effect, and b) determine whether the effect of the ACA on unintended pregnancy is mediated by access and/or affordability of contraceptives – and if so, which was more strongly impacted by the ACA. The second specific aim of the project is to assess whether the impact of the ACA on unintended pregnancy was equitable by comparing the effect of the ACA on unintended pregnancy between women of varying race/ethnicity and socioeconomic status. Aims 1 and 2 will be achieved by using cross-sectional data from multiple years (i.e., 2006-2019) of the National Survey of Family Growth, and an innovative analytic approach that combines epidemiological, time-series, and econometric methods. This work is significant because it will provide a methodological framework for future studies to investigate the health effects of policy while also informing current debates regarding the expansion, reformation, or repeal of the ACA. The applicant, Colleen MacCallum, has an MS in Biostatistics, is currently pursuing a PhD in Epidemiology at MSU, and is uniquely positioned for this fellowship because of her previous work investigating the impact of the ACA contraception mandate on unintended pregnancy, and her strong analytic background – on which she can build additional skills in econometric methods and mediation analysis. This F31 award will provide the applicant with interdisciplinary training in: 1) public policy, 2) econometric methods for policy evaluation, and 3) causal mediation analysis. Training activities will include courses, workshops, and seminar series. The proposed fellowship will be implemented in the Department of Epidemiology and Biostatistics at MSU, which is an ideal training environment due to the department’s strengths in women’s health and its strong history of mentoring and interdisciplinary collaboration. This fellowship will be mentored by: Dr. Claire Margerison (sponsor, expertise in policy impacts on women’s health), Dr. Claudia Holzman (co-sponsor, expertise in women’s health and long track record of successful mentoring), Dr. Robert Kaestner (collaborator, expertise in health policy and econometrics), Dr. Zhehui Luo (collaborator, expertise in causal inference and econometrics), and Dr. Tim Bruckner (consultant, expertise in time series modelling and health policy analysis). The proposed fellowship will equip the applicant with substantive knowledge, analytic tools, and...