Estimate DiD for a single cohort (g) and a single event time (e).

Usage

DiDge(
  inputdata,
  varnames,
  cohort_time,
  event_postperiod,
  base_event = -1,
  control_group = "all",
  return_data = FALSE,
  return_ATTs_only = TRUE
)

Arguments

inputdata: A data.table.
varnames: A list of the form varnames = list(id_name, time_name, outcome_name, cohort_name), where all four arguments of the list must be a character that corresponds to a variable name in inputdata.
cohort_time: The treatment cohort of reference.
event_postperiod: Number of time periods after the cohort time at which to estimate the DiD.
base_event: This is the base pre-period that is normalized to zero in the DiD estimation. Default is base_event=-1.
control_group: There are three possibilities: control_group="never-treated" uses the never-treated control group only; control_group="future-treated" uses those units that will receive treatment in the future as the control group; and control_group="all" uses both the never-treated and the future-treated in the control group. Default is control_group="all".
return_data: If true, this returns the treated and control differenced data. Default is FALSE.
return_ATTs_only: Return only the ATT estimates and sample sizes. Default is TRUE.

Value

A single-row data.table() containing the estimates and various statistics such as sample size. If return_data=TRUE, it instead returns a list in which the data_prepost entry is the previously-mentioned single-row data.table(), and the other argument data_prepost contains the constructed data that should be provided to OLS.

Examples

# simulate some data
simdata = SimDiD(sample_size=200)$simdata

# define the variable names as a list()
varnames = list()
varnames$time_name = "year"
varnames$outcome_name = "Y"
varnames$cohort_name = "cohort"
varnames$id_name = "id"

# estimate the ATT for cohort 2007 at event time 1
DiDge(simdata, varnames, cohort_time=2007, event_postperiod=1)
#>    Cohort EventTime BaseEvent CalendarTime    ATTge  ATTge_SE Ncontrol Ntreated
#>     <num>     <num>     <num>        <num>    <num>     <num>    <int>    <int>
#> 1:   2007         1        -1         2008 1.674411 0.2372155      151       49

# change the base period to -3
DiDge(simdata, varnames, base_event=-3, cohort_time=2007, event_postperiod=1)
#>    Cohort EventTime BaseEvent CalendarTime    ATTge  ATTge_SE Ncontrol Ntreated
#>     <num>     <num>     <num>        <num>    <num>     <num>    <int>    <int>
#> 1:   2007         1        -3         2008 1.519178 0.2446772      151       49

# use only the never-treated control group
DiDge(simdata, varnames, control_group = "never-treated", cohort_time=2007, event_postperiod=1)
#>    Cohort EventTime BaseEvent CalendarTime    ATTge  ATTge_SE Ncontrol Ntreated
#>     <num>     <num>     <num>        <num>    <num>     <num>    <int>    <int>
#> 1:   2007         1        -1         2008 1.511766 0.2896609       51       49