References & Further Reading
Difference-in-Differences
Books, articles, and resources to deepen your understanding.
The Effect: An Introduction to Research Design and Causality
Nick Huntington-Klein (2021)
Chapter 18 covers DiD in depth, from the basic 2×2 setup through rollout designs and modern estimators. The primary reference for these notes.
Causal Inference: The Mixtape
Scott Cunningham (2021)
Another excellent textbook covering DiD with detailed discussion and case studies
On the Mode of Communication of Cholera
John Snow (1855)
The classic study that used what we now call a DiD design to demonstrate cholera was spread by contaminated water, not "miasma."
Difference-in-Differences with Variation in Treatment Timing
Andrew Goodman-Bacon (2021)
Identifies the problems with using TWFE in staggered rollout designs. Shows how already-treated groups get used as comparisons, leading to bias.
Difference-in-Differences with Multiple Time Periods
Brantly Callaway & Pedro H.C. Sant'Anna (2021)
Proposes group-time treatment effects as a solution to the staggered timing problem. One of the most widely adopted modern DiD estimators.
Difference-in-Differences Designs: A Practitioner's Guide
Andrew Baker, Brantly Callaway, Scott Cunningham, Andrew Goodman-Bacon, Pedro H. C. Sant'Anna (2025)
A comprehensive guide on the application of DiD — great for understanding the landscape of recent advances.