Difference in Differences

A 3-Day Remote Seminar Taught by
Pedro H. C. Sant’Anna, Ph.D.

Read reviews of this course

To see a sample of the course slides, click here.


Difference-in-Differences (DiD) methods are widely used in the estimation of causal effects of policy interventions in the social and medical sciences. At their core, DiD methods leverage the fact that units are exposed to treatment at different points in time (or never exposed). Consequently, researchers can recover an average treatment effect by comparing outcomes from different treatment cohorts, before and after they have been exposed to treatment. A major advantage of using the DiD framework is that we can account for time trends and (time-invariant) unobserved heterogeneity when recovering causal effects.

This seminar offers a thorough introduction to classical and modern Difference-in-Differences methods. The main goal of this seminar is to enable researchers to get closer to the DiD research frontier.

Starting October 14, we are offering this seminar as a 3-day synchronous*, remote workshop. Each day will consist of a 4-hour live lecture held via the free video-conferencing software Zoom. You are encouraged to join the lecture live, but will have the opportunity to view the recorded session later in the day if you are unable to attend at the scheduled time.

Each lecture session will conclude with a hands-on exercise reviewing the content covered, to be completed on your own. An additional lab session will be held Thursday and Friday afternoons, where you can review the exercise results with the instructor and ask any questions.

*We understand that scheduling is difficult during this unpredictable time. If you prefer, you may take all or part of the course asynchronously. The video recordings will be made available within 24 hours of each session and will be accessible for four weeks after the seminar, meaning that you will get all of the class content and discussions even if you cannot participate synchronously.

Closed captioning is available for all live and recorded sessions.


MORE DETAILS ABOUT THE COURSE CONTENT

We will cover the theory and practice of DiD methods in great detail including topics such as:

  • The canonical two-periods, two-groups DiD
  • The role of covariates in DiD setups
  • DiD with variation in treatment timing
  • Design-based inference in DiD settings

At the end of the seminar, we expect that you should be comfortable and confident in using DiD methods to tackle your own research questions.


COMPUTING

This seminar will use R for the empirical examples and exercises. To participate in the hands-on exercises, you are strongly encouraged to use a computer with the most recent version of R and RStudio installed. RStudio is a front-end for R that makes it easier to work with. This software is free and available for Windows, Mac, and Linux platforms.

If you’d like to take this course but are concerned that you don’t know enough R, there are excellent online resources for learning the basics including Statistics with R. Here are our recommendations.

In case you are more comfortable with Stata, the course will also reference Stata packages that implement the same DiD tools that will be demonstrated with R, whenever such packages exist.


WHO SHOULD Register? 

If you want to learn how to conduct causal inference using difference-in-differences methods, and have a basic statistical background, this course is for you. You should have a good working knowledge of the principles and practice of multiple regression, as well as elementary statistical inference. It is also helpful to have some basic familiarity with the R programming language.


Seminar Outline

1. The potential outcome framework

2. Review of basic statistical inference

3. The canonical two-periods, two-groups DiD

               a. Role of identifying assumptions: no-anticipation and parallel trends

               b. Implementation via simple comparison of means

               c. Implementation via regressions

4. Role of covariates in DiD setups

               a. Allowing for covariate-specific trends

               b. Pitfalls of two-way fixed effects linear regression specifications

               c. Estimating treatment effects using the outcome-regression
                  approach

               d. Estimating treatment effects using the inverse-probability weighting
                  approach

               e. Estimating treatment effects using a doubly-robust approach

5. DiD with variation in treatment timing

               a. What are the causal parameters of interest?

               b. What type of parallel trends are we willing to impose?

               c. Pitfalls of two-way fixed effects linear regression specifications

               d. Recovering meaningful causal parameters

               e. Highlighting treatment effect dynamics via event-studies

               f. Highlighting other sources of treatment effect heterogeneity

6. Other DiD topics (if time allows):

               a. Design-based inference in DiD settings

               b. DiD with violations of the parallel trends assumption

               c. When is parallel trends sensitive to functional form?

               d. Distributional DiD methods

               e. Fuzzy DiD


REVIEWS OF DIFFERENCE IN DIFFERENCES

“If you want to learn DiD, this is the course. Pedro is a star in this field, and he explains classic DiD and recent developments in concise and intuitive ways.”
  Anibal Perez-Linan, University of Notre Dame

“This is an excellent course. I was already familiar with DID models, but the course provided new developments I was not aware of and that I found very useful. I will use these new methods in my work.”
  Gustavo Angeles, UNC, Chapel Hill

“This workshop was very practical with state-of-the-art content. Pedro is an excellent speaker.”
  Soumyadeep Sinharay

“Awesome blend of hands-on treatment of estimation and background. Our lecturer gave a top overview of the recent developments and literature, which I could not have digested so quickly on my own.”
  Juerg Schweri, Swiss Federal University for Vocational Education and Training

“Very nice overview of recent and important literature on a workhorse model in applied micro from one of the leading researchers in the area. Pedro was also extremely helpful and very responsive to questions.”
  Austin Bean, Temple University

“Pedro is a great instructor. I really liked that he took the time to answer people’s questions in depth and the content was well adapted to the diverse crowd.”
  Sue Marquez, The Rockefeller Foundation

“The professor was interesting and provided a good overview of the basics before jumping into more complex material.”
  Becky Dvorak, HumRRO

“The depth of knowledge illustrated by the teacher was phenomenal. Pedro was willing and able to answer a very wide field of questions on the topic clearly and in detail.”
  Robert Wishart, Wishart Research Consulting

“What I liked the most about this seminar is all theories/assumptions and estimation procedures, which were explained very clearly for conditional parallel trend in the 2×2 setting. I really learned a lot!”
  Yu Ye, Public Health Institute