Difference-in-Difference-in-Differences Method (DDD) | Estimation Methods | Stata Tutorials Topic 43

Stata Tutorials Topic 43: Difference-in-Difference-in-Differences Method (DDD) | Regression Analysis and Estimation Methods Using Stata Hi, I am Bob. Welcome to the Stata course on regression analysis and estimation methods. Today, we will continue our discussion about the difference-in-differences method. The difference-in-differences design is a powerful identification strategy for causal effects analysis. It can alleviate the omitted variable bias and help us find the causal effect of the treatment on the outcome variable. It depends on a crucial assumption, the parallel trends assumption. That is, the treatment group and the control group are similar in every aspect except that the control group did not receive the treatment. It is equivalent to saying that factors other than the treatment affect the outcomes of the control and treatment groups in the same way. In other words, the outcome variables of the treatment group and the control group have the same trend if neither of them experiences the intervention. If the parallel trends assumption is violated, we have two solutions. One is to add control variables to the model to account for the different trends between the treatment and control groups. Another method is to use the difference-in-difference-in-differences estimation (DDD). Let's show you these two approaches using an example in Stata. Please download the INJURY.dta dataset for this topic: https://drive.google.com/file/d/1yJrngM-hbLS-ZvGaCnZoAGXDfgRxpc9V/view?usp=sharing #Stata #DDD #tutorial #DID #regress #interactionterm #RegressionAnalysisandEstimationMethods #OLS #ATE #controlgroup #treatmentgroup #TreatmentEffect #Difference-in-Differences #tutorial The Stata commands in this video: *DID regress ldurat i.afchnge##i.highearn if ky==1 estimates store DID *DID with Controls describe regress ldurat i.afchnge##i.highearn male married age i.indust i.injtype if ky==1 estimates store DID2 esttab DID DID2, keep(1.afchnge 1.highearn 1.afchnge#1.highearn) star(* 0.1 ** 0.05 *** 0.01) stat(N) mtitle se *DDD regress ldurat i.afchnge##i.highearn##i.ky *Confirm the control state regress ldurat i.afchnge##i.highearn if mi==1 【Some Free Courses on My YouTube Channel】 Economics in Real Life: https://youtube.com/playlist?list=PLVnZllyvIMyQWRM_U-tpNONlgj5PvKwIm Solutions to Introductory Econometrics A Modern Approach 7th Edition: https://youtube.com/playlist?list=PLVnZllyvIMyRA-F5k-kb0RbNXd_i8oXfT Solutions to Microeconomics Theory and Applications with Calculus: https://youtube.com/playlist?list=PLVnZllyvIMyRbgoiL-XAfepq79Q11VBU3 Introductory Stata: https://youtube.com/playlist?list=PLVnZllyvIMyT8elGqkiOJmQhVfc8P-1JR Introductory Microeconomics: https://youtube.com/playlist?list=PLVnZllyvIMyTnIaoPQZHglrjoY5OkYppk Five Minute Econometrics: https://youtube.com/playlist?list=PLVnZllyvIMyQ_PeOSDVJy5YkdYaLG5-YL Five Minute Stata: https://youtube.com/playlist?list=PLVnZllyvIMyTv3CpqsxnVfhwdlQli-hSL 【國語Mandarin】現實生活中的經濟學: https://youtube.com/playlist?list=PLVnZllyvIMyRibbK32SD9CV1QoidlaJ3f 【粵語Cantonese】現實生活中的經濟學: https://youtube.com/playlist?list=PLVnZllyvIMyTlreRu86Msrwis-6f9Unze 【粵語Cantonese】微觀經濟學基礎: https://youtube.com/playlist?list=PLVnZllyvIMyQg_qgMedWyR1_OXvkw6SAL 【國語Mandarin】五分鐘計量經濟學: https://youtube.com/playlist?list=PLVnZllyvIMyRfBL-1B1-q67gYkLUl8mJq 【粵語Cantonese】五分鐘計量經濟學: https://youtube.com/playlist?list=PLVnZllyvIMyQPhDLyiPECG1VfQoL8i3uq On the Road: https://youtube.com/playlist?list=PLVnZllyvIMyRqGfGNuJTA8W-7BdEG9jay 【Become a Supporter of the channel ($2.99) to get PDF transcripts for】 1. Solutions to Microeconomics Theory and Applications with Calculus 5th Edition, 2. Solutions to Introductory Econometrics A Modern Approach 7th Edition, 3. Introductory Stata (2022), 4. Introductory Microeconomics (2022), and 5. Introductory Stata: Summary Statistics and Data Management https://www.youtube.com/channel/UCQ-qJEqT-G_O8v5atXqF1Kg/join