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  • a large coefficient in 2SLS

    Dear Profs and colleagues,

    Could you please have a look at the 2sls results and say why is a potential reason for such a huge coefficient?

    Code:
    . ivregress 2sls ln_mig_firm (immi_sh =S_tfp_lp_iv)   firm_age foreign_aff i.year i.sector i.region ,first 
    > vce(robust)
    
    First-stage regressions
    -----------------------
    
                                                         Number of obs =    26,491
                                                         F(25, 26465)  = 181421.09
                                                         Prob > F      =    0.0000
                                                         R-squared     =    0.9932
                                                         Adj R-squared =    0.9932
                                                         Root MSE      =    0.0118
    
    ------------------------------------------------------------------------------
                 |               Robust
         immi_sh | Coefficient  std. err.      t    P>|t|     [95% conf. interval]
    -------------+----------------------------------------------------------------
        firm_age |   6.38e-06   4.55e-06     1.40   0.160    -2.53e-06    .0000153
     foreign_aff |  -.0006675   .0002654    -2.51   0.012    -.0011877   -.0001472
                 |
            year |
           2011  |  -.0046915   .0000763   -61.49   0.000    -.0048411    -.004542
           2012  |  -.0188105   .0001383  -135.99   0.000    -.0190816   -.0185394
           2013  |  -.0291766   .0001304  -223.76   0.000    -.0294322    -.028921
           2014  |  -.0344718   .0001383  -249.22   0.000     -.034743   -.0342007
           2015  |   -.039164   .0001847  -212.08   0.000    -.0395259    -.038802
           2016  |   -.033093   .0001741  -190.12   0.000    -.0334342   -.0327519
           2017  |  -.0170869   .0001444  -118.37   0.000    -.0173698    -.016804
           2018  |   .0242047   .0002957    81.87   0.000     .0236252    .0247842
           2019  |   .0992518   .0008146   121.84   0.000     .0976552    .1008484
                 |
          sector |
              6  |   .0000934   .0002583     0.36   0.718    -.0004129    .0005998
              7  |   .0006499   .0002023     3.21   0.001     .0002534    .0010465
              9  |   .0005937   .0002351     2.53   0.012     .0001329    .0010546
             10  |   .0016304   .0006251     2.61   0.009     .0004052    .0028556
             11  |   .0011972   .0006038     1.98   0.047     .0000138    .0023807
             12  |   .0006344   .0003622     1.75   0.080    -.0000754    .0013443
             13  |   .0001044   .0003756     0.28   0.781    -.0006317    .0008406
                 |
          region |
              2  |  -.0182584   .0001484  -123.02   0.000    -.0185493   -.0179675
              3  |    .280337    .000202  1387.83   0.000     .2799411    .2807329
              4  |   .1460576   .0002521   579.29   0.000     .1455634    .1465517
              5  |  -.0667314    .000519  -128.59   0.000    -.0677486   -.0657142
              6  |  -.1121326   .0014834   -75.59   0.000    -.1150402    -.109225
              7  |   .0754772   .0004175   180.78   0.000     .0746588    .0762955
                 |
     S_tfp_lp_iv |  -1.49e-08   3.33e-08    -0.45   0.653    -8.02e-08    5.03e-08
           _cons |   .2246455    .000314   715.52   0.000     .2240301    .2252609
    ------------------------------------------------------------------------------
    
    
    Instrumental variables 2SLS regression            Number of obs   =     26,491
                                                      Wald chi2(25)   =       2.05
                                                      Prob > chi2     =     1.0000
                                                      R-squared       =          .
                                                      Root MSE        =      41.91
    
    ------------------------------------------------------------------------------
                 |               Robust
     ln_mig_firm | Coefficient  std. err.      z    P>|z|     [95% conf. interval]
    -------------+----------------------------------------------------------------
         immi_sh |   3559.456   7916.329     0.45   0.653    -11956.26    19075.18
        firm_age |  -.0215857   .0543908    -0.40   0.691    -.1281897    .0850183
     foreign_aff |   1.837859   5.449556     0.34   0.736    -8.843074    12.51879
                 |
            year |
           2011  |   16.70971   37.10893     0.45   0.653    -56.02246    89.44188
           2012  |   66.95652   148.8554     0.45   0.653    -224.7947    358.7077
           2013  |   103.8499   230.9159     0.45   0.653    -348.7369    556.4367
           2014  |   122.7141   272.8344     0.45   0.653    -412.0315    657.4598
           2015  |   139.4373   309.9755     0.45   0.653    -468.1036    746.9781
           2016  |   117.8588    261.917     0.45   0.653     -395.489    631.2066
           2017  |    60.9297   135.2064     0.45   0.652    -204.0699    325.9293
           2018  |  -85.96534   191.6586    -0.45   0.654    -461.6094    289.6787
           2019  |  -352.9831   785.7056    -0.45   0.653    -1892.938    1186.972
                 |
          sector |
              6  |  -.2117265   1.154057    -0.18   0.854    -2.473637    2.050184
              7  |  -2.544629    5.07718    -0.50   0.616    -12.49572    7.406461
              9  |  -1.912517    4.67503    -0.41   0.682    -11.07541    7.250373
             10  |  -6.121399   13.12657    -0.47   0.641      -31.849     19.6062
             11  |  -4.624659   9.580822    -0.48   0.629    -23.40272    14.15341
             12  |  -2.685645   5.163709    -0.52   0.603    -12.80633    7.435039
             13  |   .1726301   1.554906     0.11   0.912     -2.87493     3.22019
                 |
          region |
              2  |   65.09497   144.5012     0.45   0.652    -218.1222    348.3122
              3  |   -997.353   2219.142    -0.45   0.653    -5346.792    3352.086
              4  |  -519.5848   1156.363    -0.45   0.653    -2786.016    1746.846
              5  |   237.6837   528.1781     0.45   0.653    -797.5264    1272.894
              6  |   398.9299   887.5722     0.45   0.653     -1340.68    2138.539
              7  |  -268.7247   597.6235    -0.45   0.653    -1440.045    902.5958
                 |
           _cons |  -798.4771   1778.322    -0.45   0.653    -4283.924    2686.969
    ------------------------------------------------------------------------------
    Instrumented: immi_sh
     Instruments: firm_age foreign_aff 2011.year 2012.year 2013.year 2014.year
                  2015.year 2016.year 2017.year 2018.year 2019.year 6.sector
                  7.sector 9.sector 10.sector 11.sector 12.sector 13.sector
                  2.region 3.region 4.region 5.region 6.region 7.region
                  S_tfp_lp_iv
    
    . dataex ln_mig_firm immi_sh S_tfp_lp_iv   firm_age foreign_aff year sector region
    
    
    * Example generated by -dataex-. For more info, type help dataex
    clear
    input float(ln_mig_firm immi_sh S_tfp_lp_iv) double firm_age float foreign_aff double year float(sector region)
            0  .3650748         0  29 1 2010  3 4
     .6931472  .3646793         0  30 1 2011  3 4
            0   .343915         0  31 1 2012  3 4
            0  .3277757         0  34 1 2015  3 4
            0  .3433293         0  35 1 2016  3 4
            0  .3693548         0  36 1 2017  3 4
            0  .2298563         0  35 1 2010  9 1
            0 .22289327         0  36 1 2011  9 1
            0    .21112         0  37 1 2012  9 1
            0 .19803737         0  38 1 2013  9 1
     .6931472 .50198424         0   3 1 2010  9 3
    1.0986123  .4977463         0   4 1 2011  9 3
     .6931472  .4793266         0   5 1 2012  9 3
            0  .4701448         0   6 1 2013  9 3
     .6931472  .4650751         0   7 1 2014  9 3
     .6931472  .4563765         0   8 1 2015  9 3
     .6931472  .4846899         0  10 1 2017  9 3
            0 .54520756         0  11 1 2018  9 3
    2.0794415  .2298563         0 151 0 2010  3 1
    2.0794415 .22289327         0 152 0 2011  3 1
    1.3862944    .21112         0 153 0 2012  3 1
    1.3862944 .19803737         0 154 0 2013  3 1
     .6931472  .1918098         0 155 0 2014  3 1
     .6931472  .1883774         0 156 0 2015  3 1
    1.0986123 .19334607         0 157 0 2016  3 1
    1.3862944  .2061446         0 158 0 2017  3 1
     1.609438 .24056286         0 159 0 2018  3 1
    1.0986123  .3039402         0 160 0 2019  3 1
            0 .50198424         0  86 1 2010  3 3
            0  .4563765         0  91 1 2015  3 3
     .6931472  .4628399         0  92 1 2016  3 3
     .6931472  .4846899         0  93 1 2017  3 3
    1.0986123 .50198424         0  85 1 2010  7 3
            0 .24056286         0  78 1 2018  7 1
            0  .2298563         0  37 1 2010  3 1
            0 .22289327         0  38 1 2011  3 1
            0    .21112         0  39 1 2012  3 1
            0 .19803737         0  40 1 2013  3 1
            0  .1918098         0  41 1 2014  3 1
            0  .1882468         0  74 1 2017  3 2
            0 .21992885         0  75 1 2018  3 2
     .6931472   .278263         0  76 1 2019  3 2
            0  .1882468         0  52 1 2017  3 2
            0 .21992885         0  53 1 2018  3 2
            0   .278263         0  54 1 2019  3 2
    1.0986123 .50198424         0  38 1 2010  7 3
    1.3862944  .4977463         0  39 1 2011  7 3
            0  .4701448         0  41 1 2013  7 3
    1.0986123 .50198424         0  37 1 2010  6 3
            0  .2298563         0  39 1 2010  3 1
    1.3862944 .21017927         0  81 1 2010  3 2
     .6931472 .19334395         0  83 1 2012  3 2
            0 .18194366         0  84 1 2013  3 2
            0  .1767448         0  85 1 2014  3 2
     .6931472  .1733526         0  86 1 2015  3 2
     .6931472  .2298563         0  40 1 2010  7 1
            0  .2298563         0  92 1 2010  3 1
            0 .22289327         0  93 1 2011  3 1
            0    .21112         0  94 1 2012  3 1
            0 .19334607         0  98 1 2016  3 1
            0  .2061446         0  99 1 2017  3 1
            0 .24056286         0 100 1 2018  3 1
     .6931472  .3039402         0 101 1 2019  3 1
            0  .2298563  7794.267  53 1 2010  3 1
            0 .22289327  7557.628  54 1 2011  3 1
            0    .21112  7157.588  55 1 2012  3 1
            0 .19803737  6713.168  56 1 2013  3 1
            0  .1918098  6501.658  57 1 2014  3 1
            0  .1883774  6385.091  58 1 2015  3 1
            0 .19334607  6553.832  59 1 2016  3 1
            0 .21017927         0  56 1 2010  3 2
     .6931472 .15304422         0  53 1 2010  3 5
     .6931472 .15222874         0  54 1 2011  3 5
     .6931472  .1431196         0  55 1 2012  3 5
     .6931472 .13922645         0  56 1 2013  3 5
     .6931472 .13559788         0  57 1 2014  3 5
            0 .21017927 4804.0166  56 1 2010  3 2
     .6931472  .4977463         0  56 1 2011  3 3
    1.0986123  .4793266         0  57 1 2012  3 3
    1.0986123  .4701448         0  58 1 2013  3 3
    1.0986123  .4650751         0  59 1 2014  3 3
     .6931472  .4563765         0  60 1 2015  3 3
    1.0986123  .4846899         0  62 1 2017  3 3
     .6931472 .54520756         0  63 1 2018  3 3
            0  .6566781         0  64 1 2019  3 3
            0 .22289327         0  53 1 2011  3 1
      1.94591 .21017927         0  54 1 2010  3 2
    1.3862944 .20349567         0  55 1 2011  3 2
    1.0986123 .19334395         0  56 1 2012  3 2
    2.3025851 .18194366         0  57 1 2013  3 2
    1.7917595  .1767448         0  58 1 2014  3 2
    2.0794415  .1733526         0  59 1 2015  3 2
      1.94591 .17714684         0  60 1 2016  3 2
     .6931472 .50198424         0  52 1 2010 13 3
     .6931472  .2298563         0  53 0 2010  7 1
    1.3862944  .1918098         0  57 0 2014  7 1
    1.7917595  .1883774         0  58 0 2015  7 1
    2.0794415  .2298563         0  69 1 2010  3 1
    1.7917595 .22289327         0  70 1 2011  3 1
            0    .21112         0  71 1 2012  3 1
    end
    appreciated.
    Cheers,
    Paris

  • #2
    Hey Paris,

    it is hard to tell from the sample data. One issue seems to be the weak relationship in your first stage. The coefficient is small and insignificant on all conventional levels. In addition, I used ivreg2 to get the Kleibergen-Paap Wald F-statistic. It is close to zero (while it should be at least above 10 as a rule of thumb). This weak instrument problem could be the reason for the large coefficients.

    Best,
    Sebastian

    Comment


    • #3
      Hi Sebastian,

      Thank you for getting back to me. I believe so. The IV is not a proper one. I tried to substitute it.

      Comment

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