9.3 - Difference-in-Differences Assumptions and Proof

In this part of the Introduction to Causal Inference course, we give the formal assumptions that underlie the difference-in-differences method for causal effect estimation. Then, we use these to proof a corresponding identification result. Please post questions in the YouTube comments section. Introduction to Causal Inference Course Website: causalcourse.com Course Lectures Playlist: https://www.youtube.com/watch?v=tsYZcpuQYnE&list=PLoazKTcS0Rzb6bb9L508cyJ1z-U9iWkA0&index=60