{smcl}
{* *! version 1  2018-07-27}{...}
{viewerjumpto "Syntax" "did_multiplegt##syntax"}{...}
{viewerjumpto "Arguments" "did_multiplegt##options"}{...}
{viewerjumpto "Description" "did_multiplegt##description"}{...}
{viewerjumpto "Examples" "did_multiplegt##examples"}{...}

{title:Title}

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{cmd:did_multiplegt} {hline 2} Library of Estimators in 
Difference-in-Difference (DID) designs with multiple groups and periods.
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{marker syntax}{...}
{title:Syntax}

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{cmd:did_multiplegt (mode) Y G T D} {ifin}
[{cmd:, options}]
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{marker description}{...}
{title:Description}

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{cmd:did_multiplegt} wraps in a single command all
the DID estimators from de Chaisemartin and D'Haultfoeuille.
Depending on the {cmd:mode} argument, this command can be used to call the following estimators.
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{p 12 12}
{stata help did_multiplegt_dyn:did_multiplegt_dyn}. 
In {cmd:dyn} mode, the command computes 
heterogeneity-robust event-study DID estimators 
introduced in de Chaisemartin and D'Haultfoeuille (2024a).
Like other recently proposed DID estimators 
(csdid, didimputation, ...), these estimators 
can be used with a binary and staggered (absorbing) 
treatment. But unlike those other estimators, 
these estimators can also be used with a non-binary 
(discrete or continuous) and non-absorbing 
treatment that can increase or decrease multiple times.  
These estimators can also be used when lagged 
treatments affect the outcome.
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{p 12 12}
{stata help did_multiplegt_stat:did_multiplegt_stat}. 
In {cmd:stat} mode, the command computes 
heterogeneity-robust DID estimators introduced in de Chaisemartin and 
D'Haultfoeuille (2020) and de Chaisemartin et al. (2022). These estimators can be used with a
non-binary (discrete or continuous) and non-absorbing treatment. However, they assume 
that past  treatments do not affect the current outcome.
Finally, these estimators can be used to compute IV-DID estimators, relying on a parallel-trends assumption with respect 
to an instrumental variable rather than the treatment.
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{p 12 12}
{stata help did_had:did_had}. 
In {cmd:had} mode, the command 
computes the DID estimators 
introduced in de Chaisemartin and D'Haultfoeuille (2024b). 
These estimators can be used in heterogeneous adoption designs (HAD) 
with no stayers but some quasi stayers. 
{p_end}

{p 12 12}
{stata help did_multiplegt_old:did_multiplegt_old}. 
In {cmd:old} mode, the command computes the DID 
estimators introduced in de Chaisemartin and 
D'Haultfoeuille (2020). This mode corresponds 
to the old version of the did_multiplegt command.
We do not recommend using this mode. The three aforementioned modes are much faster, because
they do not rely on the bootstrap to compute standard errors. Moreover,
they offer more comprehensive and up to date estimation and post-estimation options.
{p_end}

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{cmd:did_multiplegt} updates 
automatically all the packages above 
(on average) every 100 runs of the command. 
Self-updates can be stopped by 
specifying the command with the {cmd:no_updates} option.
{p_end}

{marker arguments}{...}
{title:Arguments}

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{cmd:mode} is the command selector and can be only be {cmd:dyn}, {cmd:had} or {cmd:old}.
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{cmd:Y} is the outcome variable.
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{cmd:G} is the group variable.
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{cmd:T} is the time period variable.
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{cmd:D} is the treatment variable.
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{cmd:options} is a pass-through 
and can include all the options of the 
command called with {cmd:mode}. It can 
include the {cmd:no_updates} option, which 
will apply only for {cmd:did_multiplegt} and 
will not be passed onto the {cmd:mode} options.
{p_end}

{marker Example}{...}
{title:Example: Estimating the effect of union membership on wages}

Loading the worker-year level data from Vella and Verbeek (1998):
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{stata bcuse wagepan}
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Computing DID_M from de Chaisemartin and D'Haultfoeuille (2020):
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{stata did_multiplegt (old) lwage nr year union, breps(100) cluster(nr)}
{p_end}
{p 4 8}
{stata did_multiplegt (stat) lwage nr year union, exact_match}
{p_end}


Computing 5 dynamic effects and 2 placebos using DID_l from de Chaisemartin and D'Haultfoeuille (2024a):
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{stata did_multiplegt (dyn) lwage nr year union, effects(5) placebo(2) graph_off}
{p_end}

{title:References}

{p 4 8}
de Chaisemartin, C and D'Haultfoeuille, X (2020). American Economic Review, vol. 110, no. 9.
{browse "https://www.aeaweb.org/articles?id=10.1257/aer.20181169":Two-Way Fixed Effects Estimators with Heterogeneous Treatment Effects}.
{p_end}
{p 4 8}
de Chaisemartin, C, D'Haultfoeuille, X, Pasquier, F, Vazquez‐Bare, G (2022). 
{browse "https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4011782":Difference-in-Differences for Continuous Treatments and Instruments with Stayers}.
{p_end}
{p 4 8}
de Chaisemartin, C and D'Haultfoeuille, X (2024a). Review of Economics and Statistics, 1-45.
{browse "https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3731856":Difference-in-Differences Estimators of Intertemporal Treatment Effects}.
{p_end}
{p 4 8}
de Chaisemartin, C and D'Haultfoeuille, X (2024b).
{browse "https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4284811":Two-way Fixed Effects and Differences-in-Differences Estimators in Heterogeneous Adoption Designs}.
{p_end}
{p 4 8}
Vella, F. and Verbeek, M. 1998. Journal of Applied Econometrics 13(2), 163–183.
{browse "https://onlinelibrary.wiley.com/doi/abs/10.1002/(SICI)1099-1255(199803/04)13:2%3C163::AID-JAE460%3E3.0.CO;2-Y":Whose wages do unions raise? a dynamic model of unionism and wage rate determination for young men}.
{p_end}

{title:Authors}

{p 4 4}
Clément de Chaisemartin, Economics Department, Sciences Po, France.
{p_end}
{p 4 4}
Diego Ciccia, Sciences Po, France.
{p_end}
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Xavier D'Haultfoeuille, CREST-ENSAE, France.
{p_end}
{p 4 4}
Felix Knau, Sciences Po, France.
{p_end}
{p 4 4}
Felix Pasquier, CREST-ENSAE, France.
{p_end}
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Mélitine Malézieux, Stockholm School of Economics, Sweden.
{p_end}
{p 4 4}
Doulo Sow, Sciences Po, France.
{p_end}
{p 4 4}
Gonzalo Vazquez-Bare, UCSB, USA.
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{title:Contact}

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Mail:
{browse "mailto:chaisemartin.packages@gmail.com":chaisemartin.packages@gmail.com}
{p_end}

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GitHub:
{browse "https://github.com/chaisemartinPackages":chaisemartinPackages} 
or individual packages ({browse "https://github.com/chaisemartinPackages/did_multiplegt_dyn":did_multiplegt_dyn} 
| {browse "https://github.com/chaisemartinPackages/did_multiplegt_stat":did_multiplegt_stat}
| {browse "https://github.com/chaisemartinPackages/did_had":did_had} 
| {browse "https://github.com/chaisemartinPackages/did_multiplegt":did_multiplegt}).
{p_end}