An explanation and data example of a simple Difference-in-Difference model, with an example in Stata.
Link to excellent new book - Causal Inference: The Mixtape by Scott Cunningham
(https://amzn.to/3fTxdvg)
Classic Article by Card and Kruger using a Diff-in-Diff approach to study impact of changing the minimum wage (https://www.nber.org/papers/w4509)