An intuitive introduction to Difference-in-Differences

Difference-in-Differences is one of the most widely applied methods for estimating causal effects of programs when the program was not implemented as a randomized controlled trial.

In this video I describe the situations where the method is applicable and give you the intuition behind it. I also explain how and why you might want to use regression to estimate diff-in-diff effects. Throughout, I talk about the key assumption required for the diff-in-diff estimate to be valid.

Intended audience: Folks who have had some exposure to linear regression models, but want to learn more statistical methods.

[pedrocolangelo]

This is probably one of the best videos on this subject that I've ever seen. Thanks!!

[anz-tf]

One of the best and most lucid explanations of the DID method. Thank you for this, Doug. Especially how you explain the intuition behind how the calculation of the DID estimate done by hand is same as that estimated by the regression model. And the part where you elaborate on the simple benefits of using a regression for a DID model, is great.
Really appreciate it that you having shared your understanding here.

[monicamu]

When I watched the video for the first time, I was totally lost. During the second time, I took pauses in between to allow myself take more time to understand your super intelligent and super long sentences. It is so much clearer now. Thank you so much!

[SalehBabazadeh]

Thank you so much Doug! I just wanted to encourage you for keeping up this great job. your videos are awesome and I believe, they are being used by different people in different field.

[AkbarinSeoul]

Youtube needs more high-quality videos like this. Thank you, Mr. Doug!

[larryGizza]

This is such a clear and helpful video. I’m taking an exam in an hour and doing last minute double checks. This makes me feel more confident, thank you

[sharonie]

Best Diff-in-diff course I have learned. Thanks!

[FromMeToMe_]

Thank you so much for making this video. I am doing a master in Epidemiology now and I find this video, especially the example so valuable.

[bl.l]

Your videos have been vital for understanding the contents of my statistics course for me! So far, I've supplemented every new concept with your videos. Sometimes, I even watch your video first and then do the readings. Please keep doing these videos!

[sembilanbereguler]

Based on regression result (at 8:59), what is criteria to reject null hypothesis (to say that the effect of lunch program is statistically significant)?

[brothermalcolm]

Absolutely brilliant tutorial, first result returned, wish youtube was always this helpful!

[instablm]

Can't tell you how useful your videos are. Thanks for passing on the knowledge!

[xb]

way more intuative than previously thought, well put thanks

[zaraazami]

Thank you so much! This video was waaay much helpful than reading pages and pages on DD! Very clear and to the point! Thank you!!

[Josefk]

Excellent explanation in 12 minutes. Thank you

[Itachi]

thanks a lot for this clear explanation, you dont know how much it helped me

[kevinvandenbrink]

Thanks for the video, really helped me in my finance research. Just one thing when you talk about the dummy variable Dtr, I think it takes 1 if the person is in the treatment group and 0 if the person is the control group. 

[thefadingmoonlight]

Thank you so much for uploading this! I had looked online at DID and was confused. This made it so easy to understand and apply.

[marben]

Thank you very much Doug.
It helped me to analyse my data (pooled cross section).

[techierealestate]

Clear and right to the point. I always wondered why the multiplication coefficient is the DD coeff, Now I know :D