# Card and Krueger

open "/Users/jcaceres/Google Drive/jcd/carlos3/2014_2015/Aplicada/Week11/ck_exercise.gdt"

# CAMBIAN LOS SALARIOS?
smpl NJ = 1 --restrict
summary WAGE_ST --by=after --simple
smpl NJ = 0 --restrict --replace
summary WAGE_ST --by=after --simple
smpl full

# Outcome variable: average full-time equivalent employment
# employment before and after in NJ and Penn
smpl NJ = 1 --restrict
summary EMPTOT --by=after --simple
smpl NJ = 0 --restrict --replace
summary EMPTOT --by=after --simple
smpl full

# Employment in Pennsylvania restaurants is somewhat higher than in New Jersey
# in February but falls by November. Employment in New Jersey, in contrast,
# increases slightly.

# (1) First Comparison: NJ vs PA in period 2 
smpl after=1 --restrict
summary EMPTOT --by=NJ --simple
ols EMPTOT const NJ --robust
genr d2=$coeff
smpl full

# (2) Second Comparison: NJ before and after
smpl NJ=1 --restrict
summary EMPTOT --by=after --simple
ols EMPTOT const after --robust
genr dt=$coeff
smpl full


# (1C) First Comparison: AJUSTAR LAS DIFERENCIAS DESPUES DE LA REFORMA CON LAS DIFERENCIAS ANTES DE LA REFORMA 
smpl after=0 --restrict
summary EMPTOT --by=NJ --simple
ols EMPTOT const NJ --robust
genr d1=$coeff
smpl full

genr DD1=d2[2]-d1[2]

# (2C) Second Comparison: NJ before and after: AJUSTAR EL CAMBIO EN EL TIEMPO POR LA VAR EN EL TIEMPO EN PENN
smpl NJ=0 --restrict
summary EMPTOT --by=after --simple
ols EMPTOT const after --robust
genr dc=$coeff
smpl full

genr DD2=dt[2]-dc[2]

#DID
genr NJafter = NJ*after
ols EMPTOT const NJ after NJafter --robust