Estimating the Impact of Targeted Public Policies with Limited Data

Many public policies aim to support (or change the behavior of) a specific, targeted sub-group of the population. To measure the causal impacts of such policies, social scientists use quasi-experimental methods of policy evaluation, but are often hampered by data availability issues, especially regarding targeted populations, who are often disadvantaged and/or vulnerable. We use power calculations to quantify the challenge of detecting a policy’s impact on a small minority population based on population level data, using the impact of abortion bans on economic welfare as an example. We provide insight into this challenge and a roadmap for how researchers can calculate, ex-ante, whether their study is sufficiently powered to detect reasonably meaningful effect sizes.