{
  "citation": "Callaway, B. and Sant'Anna, P. H. C. (2021). Difference-in-Differences with Multiple Time Periods. Journal of Econometrics 225(2): 200-230. Cells from the did R package's documented example on its mpdta data (a software reference benchmark, not a table of the paper).",
  "deviation_evidence": null,
  "doi": "10.1016/j.jeconom.2020.12.001",
  "excerpt": "2004 2004 -0.0105 0.0246",
  "independent": null,
  "item_set": null,
  "kind": "paper",
  "known_deviation": null,
  "licence": "did package documentation (GPL-2); cited, not reproduced.",
  "locator": "summary(out), 'Group-Time Average Treatment Effects': Group 2004, Time 2004, ATT(g,t) and Std. Error",
  "metric": null,
  "n_items": null,
  "page": "did package home page (pkgdown, version badge 2.5.1), mpdta example: package documentation example, not a page of the article",
  "read_copy_sha256": "c80dc726b2bafc59c89d6c3bd22f4f717833d2fedb14388911ac7f369391c558",
  "retrieved_at": "2026-10-15",
  "se": 0.0246,
  "se_as_published": "0.0246",
  "source_id": "callaway_santanna_2021.mpdta_att_gt.g2004_t2004.paper",
  "tolerance_reason": null,
  "units": "log county teen employment",
  "url": "https://bcallaway11.github.io/did/",
  "value": -0.0105,
  "value_as_published": "-0.0105",
  "verified_by": "primary_source",
  "verified_note": "The did package's pkgdown home page (version badge 2.5.1), section on mpdta: summary(out) prints 'Group-Time Average Treatment Effects' (Group, Time, ATT(g,t), Std. Error) and summary(aggte(out, type = 'dynamic')) prints the overall event-study ATT. Read from the HTML text on 2026-10-15. The SEs are multiplier-bootstrap SEs and differ from the 2026-10-14 research note's copy (0.0243 and 0.0203 there, 0.0246 and 0.0219 now), so they are recorded and never required. The point estimates are deterministic group means; the SEs are multiplier-bootstrap draws, recorded and never required (the target's SE policy). Recorded before the tool was run on these cells: the cells were committed in the pending spec (75c3415) and the tool probed only after that commit."
}