Generalized Difference-in-Differences

Details

• Personal Author:
  Richardson, David B. ; Tchetgen Tchetgen, Eric J. ; Ye, Ting
• Description:
  Difference-in-differences (DID) analyses are used in a variety of research areas as a strategy for estimating the causal effect of a policy, program, intervention, or environmental hazard (hereafter, treatment). The approach offers a strategy for estimating the causal effect of a treatment using observational (i.e., nonrandomized) data in which outcomes on each study unit have been measured both before and after treatment. To identify a causal effect, a DID analysis relies on an assumption that confounding of the treatment effect in the pretreatment period is equivalent to confounding of the treatment effect in the post treatment period. We propose an alternative approach that can yield identification of causal effects under different identifying conditions than those usually required for DID. The proposed approach, which we refer to as generalized DID, has the potential to be used in routine policy evaluation across many disciplines, as it essentially combines two popular quasiexperimental designs, leveraging their strengths while relaxing their usual assumptions. We provide a formal description of the conditions for identification of causal effects, illustrate the method using simulations, and provide an empirical example based on Card and Krueger's landmark study of the impact of an increase in minimum wage in New Jersey on employment. [Description provided by NIOSH]
• Subjects:
  Cohort Studies Epidemiology Occupational Health Safety
• Keywords:
  Author Keywords: Regression Analysis Cohort Studies Instrumental Variables Regression Analysis Statistical Quality Control Unmeasured Confounding
• ISSN:
  1044-3983
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  8 pdf pages
• Volume:
  34
• Issue:
  2
• NIOSHTIC Number:
  nn:20067445
• Citation:
  Epidemiology 2023 Mar; 34(2):167-174
• Contact Point Address:
  David Richardson, Department of Environmental and Occupational Health, Public Health, University California, 653 East Peltason, Irvine, CA 92697
• Email:
  david.richardson@uci.edu
• Federal Fiscal Year:
  2023
• Performing Organization:
  University of North Carolina-Chapel Hill
• Peer Reviewed:
  True
• Start Date:
  20190801
• Source Full Name:
  Epidemiology
• End Date:
  20220731
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:7ea0c812341a0a21d12962cbd392961356081fb5ac39a2e6b6158cb817e8197b3a9861c39bc4a0b38ef956c1b8596684eab7478ce93cc33552a81564d92a9afa
• Download URL:
  https://stacks.cdc.gov/view/cdc/230834/cdc_230834_DS1.pdf
• File Type:
  [PDF - 590.08 KB ]