Table 11 Sept 2026From “Staggered difference-in-differences needs a cohort-time estimand”

Why must causal inference name the cohort-time estimand before running regressions?

Table 1Why must causal inference name the cohort-time estimand before running regressions?

Field	Question	Why it matters
Cohort	Which units first receive treatment in this group?	Treatment timing is part of the object.
Calendar time	In which period is the outcome observed?	A cohort can have different effects over time.
Event time	How far before or after treatment is the period?	Dynamic effects are not the same as one post-period average.
Comparison	Which untreated or not-yet-treated units provide the contrast?	Already-treated units may not be valid controls for a later cohort.
Outcome	What is measured, in which unit, and at what horizon?	A coefficient cannot repair an unclear outcome.
Aggregation	Which cohort-time effects are combined, and with what weights?	The overall number depends on the aggregation target.
Inference	Where was treatment assigned, and where should uncertainty be clustered?	Precision is part of the design, not an afterthought.

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Source: Table from this essay. Sources and interpretation are given in the article.

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From the essay

From the research bench

Staggered difference-in-differences needs a cohort-time estimand

When treatment starts at different times, name the cohort-time effect and aggregation target before interpreting a familiar fixed-effects coefficient.

1 Sept 2026

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Isoglu, S. (2026). Why must causal inference name the cohort-time estimand before running regressions? [Table]. isoglu.com. https://isoglu.com/insights/exhibits/isoglu-2026-staggered-difference-in-differences-needs-a-cohort-time-estimand-fig01/

BibTeX

@misc{isoglu-2026-staggered-difference-in-differences-needs-a-cohort-time-estimand-fig01,
  author = {Isoglu, Sinan},
  title = {{Why must causal inference name the cohort-time estimand before running regressions?}},
  year = {2026},
  howpublished = {Table 1, isoglu.com},
  url = {https://isoglu.com/insights/exhibits/isoglu-2026-staggered-difference-in-differences-needs-a-cohort-time-estimand-fig01/},
  note = {From the essay {Staggered difference-in-differences needs a cohort-time estimand}}
}

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