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  • Formulate institutions variable in 2SLS regression

    I need help in how to formulate institutions variables in 2SLS regression using the ivreg2 command. Thanks

  • #2
    ivreg2 is from SSC (FAQ Advice #12). Do you mean instrumental variables? The syntax does not differ much from ivregress.

    Code:
    webuse hsng2, clear
    *ENDOGENOUS VAR (RED), INSTRUMENTS (BLUE)
    ivregress 2sls rent pcturban (hsngval = faminc i.region)
    ivreg2 rent pcturban (hsngval = faminc i.region)
    Res.:

    Code:
     
    . ivregress 2sls rent pcturban (hsngval = faminc i.region)
    
    Instrumental variables (2SLS) regression          Number of obs   =         50
                                                      Wald chi2(2)    =      90.76
                                                      Prob > chi2     =     0.0000
                                                      R-squared       =     0.5989
                                                      Root MSE        =     22.166
    
    ------------------------------------------------------------------------------
            rent |      Coef.   Std. Err.      z    P>|z|     [95% Conf. Interval]
    -------------+----------------------------------------------------------------
         hsngval |   .0022398   .0003284     6.82   0.000     .0015961    .0028836
        pcturban |    .081516   .2987652     0.27   0.785     -.504053     .667085
           _cons |   120.7065   15.22839     7.93   0.000     90.85942    150.5536
    ------------------------------------------------------------------------------
    Instrumented:  hsngval
    Instruments:   pcturban faminc 2.region 3.region 4.region
    
    .
    . ivreg2  rent pcturban (hsngval = faminc i.region)
    
    IV (2SLS) estimation
    --------------------
    
    Estimates efficient for homoskedasticity only
    Statistics consistent for homoskedasticity only
    
                                                          Number of obs =       50
                                                          F(  2,    47) =    42.66
                                                          Prob > F      =   0.0000
    Total (centered) SS     =     61243.12                Centered R2   =   0.5989
    Total (uncentered) SS   =      2816856                Uncentered R2 =   0.9913
    Residual SS             =  24565.71669                Root MSE      =    22.17
    
    ------------------------------------------------------------------------------
            rent |      Coef.   Std. Err.      z    P>|z|     [95% Conf. Interval]
    -------------+----------------------------------------------------------------
         hsngval |   .0022398   .0003284     6.82   0.000     .0015961    .0028836
        pcturban |    .081516   .2987652     0.27   0.785     -.504053     .667085
           _cons |   120.7065   15.22839     7.93   0.000     90.85942    150.5536
    ------------------------------------------------------------------------------
    Underidentification test (Anderson canon. corr. LM statistic):          27.364
                                                       Chi-sq(4) P-val =    0.0000
    ------------------------------------------------------------------------------
    Weak identification test (Cragg-Donald Wald F statistic):               13.298
    Stock-Yogo weak ID test critical values:  5% maximal IV relative bias    16.85
                                             10% maximal IV relative bias    10.27
                                             20% maximal IV relative bias     6.71
                                             30% maximal IV relative bias     5.34
                                             10% maximal IV size             24.58
                                             15% maximal IV size             13.96
                                             20% maximal IV size             10.26
                                             25% maximal IV size              8.31
    Source: Stock-Yogo (2005).  Reproduced by permission.
    ------------------------------------------------------------------------------
    Sargan statistic (overidentification test of all instruments):          11.288
                                                       Chi-sq(3) P-val =    0.0103
    ------------------------------------------------------------------------------
    Instrumented:         hsngval
    Included instruments: pcturban
    Excluded instruments: faminc 2.region 3.region 4.region
    ------------------------------------------------------------------------------

    Comment


    • #3
      Yes, I mean instrumental variables.

      Do you have an idea what instruments should I use for institutions and they are exogenous?

      Comment


      • #4
        That is very subject-specific. You need to consult past studies or someone knowledgeable about the subject.

        Comment


        • #5
          Yes, I agree with you. Thanks Andrew.

          I have another question, If I want to perform many IVreg equations, changing the main independent variable in each equation. How can I do this? then I want to collect all my equations in one results table to show all the regressions.

          Comment


          • #6
            Code:
            ssc install estout, replace
            Code:
            webuse hsng2, clear
            set seed 06122021
            forval i=1/5{
                gen indvar`i' = pcturban+ runiformint(0, 20)
            }
            *START HERE
            eststo clear
            local estimates
            foreach var of varlist  indvar1-indvar5{
                rename `var' indvar 
                eststo `var': ivreg2 rent indvar  (hsngval = faminc i.region)
                local estimates "`estimates' `var'"
                rename indvar `var'
            }
            esttab `estimates', keep(indvar)  mlab(`estimates') nonumbers coeflab(indvar "Coefficient")
            Res.:

            Code:
            . esttab `estimates', keep(indvar)  mlab(`estimates') nonumbers coeflab(indvar "Coefficient")
            
            --------------------------------------------------------------------------------------------
                              indvar1         indvar2         indvar3         indvar4         indvar5   
            --------------------------------------------------------------------------------------------
            Coefficient         0.154         0.00972           0.102          0.0103         -0.0128   
                               (0.60)          (0.04)          (0.34)          (0.04)         (-0.05)   
            --------------------------------------------------------------------------------------------
            N                      50              50              50              50              50   
            --------------------------------------------------------------------------------------------
            t statistics in parentheses
            * p<0.05, ** p<0.01, *** p<0.001

            Comment

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