This technical report documents some of the key assumptions underlying the analysis described in Thomas (“A Benefit-Cost Assessment of Three Strategies to Prevent Unintended Pregnancy.” Brookings Working Paper, 2011), which presents results from benefit-cost simulations of a mass media campaign encouraging contraceptive use, an evidence-based teen pregnancy prevention program, and an expansion in access to family planning services provided via Medicaid. These simulations are performed using FamilyScape, which is an agent-based simulation tool that allows the user to model the impacts of policy changes on family-formation outcomes. Each policy’s effects are estimated by comparing the results of simulations that were conducted under FamilyScape’s baseline assumptions to the results of simulations that were conducted using an alternative set of assumptions regarding the presumed effects of the policy in question on contraceptive use and/or sexual behavior. See Thomas and Monea (2009) for a thorough treatment of the simulation model’s baseline assumptions. In this report, I detail the key assumptions that underpin each of the policy simulations. More specifically, I discuss my assumptions regarding the costs and effects of each simulated policy. I do not discuss here the way in which these policies’ estimated benefits are monetized. Given the complexity of this topic, it is addressed in a separate report that is co-authored by Emily Monea (2011). I begin the discussion below by describing the simulations of a teen pregnancy prevention program, after which I discuss the simulations of expanded access to Medicaid-funded family planning services and a mass media campaign. I conclude by addressing a variety of technical issues that are relevant for all three sets of policy simulations.