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Re: st: RE: omitted constant with ivregress 2sls but not with ivregress gmm or ivreg


From   pablo martinelli <pab.martinelli@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: omitted constant with ivregress 2sls but not with ivregress gmm or ivreg
Date   Tue, 29 Oct 2013 17:54:54 +0100

Now, with ivregress and small sample adjustment.

. ivregress gmm lnrtw240w tpr eshare avrentp sharecrop tenant
nonagremp wheatshare wheatyield piemontevalledaosta liguria lombardia
trentinoaltoadige veneto emilia toscana lazio abruzzi campania puglie
>  lucania calabria sicilia sardegna avmrain cvavmrain rainwin rainspr rainsum rainaut rainwin2 rainspr2 rainsum2 rainaut2 cvrainwin cvrainspr cvrainsum cvrainaut rainintwin rainintspr rainintsum raini
> ntaut cvrainintwin cvrainintspr cvrainintsum cvrainintaut height1 dislivello newslope latitude (LabnewLand3=lnpop31land), first robust small

First-stage regressions
-----------------------

                                                  Number of obs   =        727
                                                  F(  50,    676) =     368.73
                                                  Prob > F        =     0.0000
                                                  R-squared       =     0.9367
                                                  Adj R-squared   =     0.9320
                                                  Root MSE        =     0.1811

------------------------------
------------------------------------------------
             |               Robust
 LabnewLand3 |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
         tpr |  -.0752534    .030686    -2.45   0.014    -.1355048   -.0150021
      eshare |  -.2042971   .0787484    -2.59   0.010     -.358918   -.0496762
     avrentp |   2.59e-06   7.47e-06     0.35   0.729    -.0000121    .0000173
   sharecrop |   .1223223   .0690329     1.77   0.077    -.0132225    .2578671
      tenant |   .1070509   .1124441     0.95   0.341    -.1137308    .3278327
   nonagremp |  -.0185542   .0009113   -20.36   0.000    -.0203435   -.0167649
  wheatshare |   .2611341   .0944493     2.76   0.006     .0756848    .4465834
  wheatyield |   .0077474   .0026325     2.94   0.003     .0025786    .0129162
piemonteva~a |   .1687091   .0581959     2.90   0.004     .0544426    .2829756
     liguria |   .1656128   .0810158     2.04   0.041     .0065398    .3246857
   lombardia |    .051234   .0601551     0.85   0.395    -.0668793    .1693473
trentinoal~e |   .1392318   .0809547     1.72   0.086     -.019721    .2981846
      veneto |  -.0195738   .0605925    -0.32   0.747    -.1385459    .0993983
      emilia |  -.0295481   .0423374    -0.70   0.485    -.1126767    .0535805
     toscana |   .0268248   .0436844     0.61   0.539    -.0589485    .1125982
       lazio |   .0405166   .0498447     0.81   0.417    -.0573524    .1383856
     abruzzi |  -.1850101   .0471699    -3.92   0.000    -.2776273   -.0923929
    campania |   -.007703   .0852096    -0.09   0.928    -.1750103    .1596043
      puglie |  -.2555594   .0761643    -3.36   0.001    -.4051065   -.1060124
     lucania |  -.1024758   .0858727    -1.19   0.233    -.2710851    .0661336
    calabria |  -.2699014   .0986603    -2.74   0.006    -.4636189    -.076184
     sicilia |  -.4293593   .1652127    -2.60   0.010     -.753751   -.1049676
    sardegna |  -.4646977   .0892632    -5.21   0.000    -.6399643   -.2894312
     avmrain |  -.0081846   .0161084    -0.51   0.612    -.0398132     .023444
   cvavmrain |   .0811425    .192954     0.42   0.674    -.2977187    .4600036
     rainwin |   .0013707    .001745     0.79   0.432    -.0020556     .004797
     rainspr |  -.0015337   .0015158    -1.01   0.312      -.00451    .0014426
     rainsum |    .001587   .0014179     1.12   0.263    -.0011969     .004371
     rainaut |   .0022904   .0014189     1.61   0.107    -.0004955    .0050763
    rainwin2 |   1.97e-07   8.11e-07     0.24   0.808    -1.40e-06    1.79e-06
    rainspr2 |   1.39e-06   5.14e-07     2.71   0.007     3.83e-07    2.40e-06
    rainsum2 |  -2.37e-07   6.17e-07    -0.38   0.701    -1.45e-06    9.75e-07
    rainaut2 |  -2.03e-06   8.34e-07    -2.43   0.015    -3.67e-06   -3.93e-07
   cvrainwin |  -.1337135   .0910987    -1.47   0.143    -.3125838    .0451569
   cvrainspr |  -.0919449   .1411574    -0.65   0.515    -.3691047    .1852148
   cvrainsum |   .0620552   .0583617     1.06   0.288    -.0525368    .1766472
   cvrainaut |  -.0228216   .1275591    -0.18   0.858    -.2732812     .227638
  rainintwin |  -.0038742     .01052    -0.37   0.713      -.02453    .0167816
  rainintspr |    .025346   .0082647     3.07   0.002     .0091184    .0415735
  rainintsum |  -.0158319   .0053415    -2.96   0.003    -.0263199   -.0053438
  rainintaut |  -.0026335    .008307    -0.32   0.751    -.0189442    .0136772
cvrainintwin |   .1142515   .1082358     1.06   0.292    -.0982673    .3267703
cvrainintspr |  -.1338668    .071614    -1.87   0.062    -.2744795    .0067459
cvrainintsum |  -.0174779   .0458837    -0.38   0.703    -.1075696    .0726138
cvrainintaut |   -.047752   .0917345    -0.52   0.603    -.2278708    .1323668
     height1 |  -.0000976   .0000593    -1.65   0.100    -.0002141    .0000189
  dislivello |  -.0001469   .0001313    -1.12   0.263    -.0004047    .0001108
    newslope |   36.73272   10.35384     3.55   0.000     16.40318    57.06227
    latitude |   .0000167   .0002471     0.07   0.946    -.0004684    .0005018
 lnpop31land |   .8216411   .0354665    23.17   0.000     .7520034    .8912789
       _cons |  -.5036778     1.1633    -0.43   0.665    -2.787793    1.780437
------------------------------------------------------------------------------


Instrumental variables (GMM) regression                Number of obs =     727
                                                       F( 50,   676) =  140.06
                                                       Prob > F      =  0.0000
                                                       R-squared     =  0.8935
                                                       Adj R-squared =  0.8857
GMM weight matrix: Robust                              Root MSE      =  .33169

------------------------------------------------------------------------------
             |               Robust
   lnrtw240w |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
 LabnewLand3 |   .7296731   .0497567    14.66   0.000      .631977    .8273693
         tpr |    .150806   .0334861     4.50   0.000     .0850568    .2165553
      eshare |  -.5659457   .1519374    -3.72   0.000    -.8642715   -.2676198
     avrentp |   .0001132   .0000138     8.20   0.000     .0000861    .0001403
   sharecrop |  -.3001512   .1206596    -2.49   0.013    -.5370638   -.0632387
      tenant |  -.0879874    .189356    -0.46   0.642     -.459784    .2838091
   nonagremp |   .0044146   .0010269     4.30   0.000     .0023983    .0064309
  wheatshare |   .2725696   .2060365     1.32   0.186    -.1319787     .677118
  wheatyield |    .013572   .0050023     2.71   0.007     .0037501    .0233938
piemonteva~a |   .3870626   .1256582     3.08   0.002     .1403354    .6337899
     liguria |  -.7231312    .177222    -4.08   0.000    -1.071103   -.3751595
   lombardia |   .0804358   .1303098     0.62   0.537    -.1754248    .3362963
trentinoal~e |   .4460556   .1978474     2.25   0.024     .0575863    .8345249
      veneto |    .200405   .1295511     1.55   0.122     -.053966    .4547759
      emilia |  -.1549017   .0837739    -1.85   0.065    -.3193899    .0095866
     toscana |  -.2256237   .0758452    -2.97   0.003    -.3745442   -.0767033
       lazio |   .2176652   .0869598     2.50   0.013     .0469214     .388409
     abruzzi |   .4261649   .0871011     4.89   0.000     .2551437     .597186
    campania |   .5052329   .1388043     3.64   0.000     .2326936    .7777722
      puglie |   .7343379   .1361629     5.39   0.000     .4669849    1.001691
     lucania |   .1794245   .1694788     1.06   0.290    -.1533436    .5121925
    calabria |   .2868967   .2000426     1.43   0.152    -.1058828    .6796763
     sicilia |   .4136089   .3240687     1.28   0.202    -.2226934    1.049911
    sardegna |  -.1242169   .1776566    -0.70   0.485     -.473042    .2246081
     avmrain |   .0922622   .0309448     2.98   0.003     .0315027    .1530217
   cvavmrain |   .1573777   .2889331     0.54   0.586    -.4099365    .7246919
     rainwin |  -.0085693   .0029066    -2.95   0.003    -.0142763   -.0028624
     rainspr |    -.00659   .0029553    -2.23   0.026    -.0123927   -.0007873
     rainsum |  -.0082152   .0028471    -2.89   0.004    -.0138055    -.002625
     rainaut |  -.0064073   .0028704    -2.23   0.026    -.0120433   -.0007713
    rainwin2 |   7.00e-07   1.46e-06     0.48   0.632    -2.17e-06    3.57e-06
    rainspr2 |  -1.61e-06   1.45e-06    -1.11   0.269    -4.46e-06    1.24e-06
    rainsum2 |  -6.10e-07   1.41e-06    -0.43   0.665    -3.37e-06    2.15e-06
    rainaut2 |  -1.55e-06   1.44e-06    -1.07   0.284    -4.39e-06    1.29e-06
   cvrainwin |   .4861783   .1804904     2.69   0.007     .1317891    .8405675
   cvrainspr |  -.2146707    .216391    -0.99   0.322    -.6395499    .2102085
   cvrainsum |  -.0934008   .1334395    -0.70   0.484    -.3554065    .1686048
   cvrainaut |  -.1363144   .2152489    -0.63   0.527    -.5589511    .2863223
  rainintwin |  -.0395274   .0195334    -2.02   0.043    -.0778809    -.001174
  rainintspr |   .0195541   .0189044     1.03   0.301    -.0175643    .0566724
  rainintsum |  -.0010367   .0127531    -0.08   0.935    -.0260772    .0240038
  rainintaut |   .0029407    .016421     0.18   0.858    -.0293015     .035183
cvrainintwin |  -.2216308   .1724045    -1.29   0.199    -.5601434    .1168818
cvrainintspr |   .1727809   .1478761     1.17   0.243    -.1175708    .4631327
cvrainintsum |   .1093444    .095904     1.14   0.255    -.0789611    .2976499
cvrainintaut |  -.0724951   .1758545    -0.41   0.680    -.4177818    .2727916
     height1 |  -.0005161   .0001081    -4.77   0.000    -.0007284   -.0003038
  dislivello |  -.0000686   .0002501    -0.27   0.784    -.0005596    .0004224
    newslope |  -4.832518   18.35956    -0.26   0.792    -40.88113    31.21609
    latitude |   .0000422   .0004502     0.09   0.925    -.0008417    .0009262
       _cons |  -2.906064   2.088086    -1.39   0.164    -7.005977    1.193849
------------------------------------------------------------------------------
Instrumented:  LabnewLand3
Instruments:   tpr eshare avrentp sharecrop tenant nonagremp wheatshare
               wheatyield piemontevalledaosta liguria lombardia
               trentinoaltoadige veneto emilia toscana lazio abruzzi
               campania puglie lucania calabria sicilia sardegna avmrain
               cvavmrain rainwin rainspr rainsum rainaut rainwin2 rainspr2
               rainsum2 rainaut2 cvrainwin cvrainspr cvrainsum cvrainaut
               rainintwin rainintspr rainintsum rainintaut cvrainintwin
               cvrainintspr cvrainintsum cvrainintaut height1 dislivello
               newslope latitude lnpop31land

2013/10/29 pablo martinelli <pab.martinelli@gmail.com>:
> This fact is even more puzzling when one
> considers the following results with gmm:
>
>
> . ivregress gmm lnrtw240w tpr eshare avrentp sharecrop tenant
> nonagremp wheatshare wheatyield piemontevalledaosta liguria lombardia
> trentinoaltoadige veneto emilia toscana lazio abruzzi campania puglie
>>  lucania calabria sicilia sardegna avmrain cvavmrain rainwin rainspr rainsum rainaut rainwin2 rainspr2 rainsum2 rainaut2 cvrainwin cvrainspr cvrainsum cvrainaut rainintwin rainintspr rainintsum raini
>> ntaut cvrainintwin cvrainintspr cvrainintsum cvrainintaut height1 dislivello newslope latitude (LabnewLand3=lnpop31land), first robust
>
> First-stage regressions
> -----------------------
>
>                                                   Number of obs   =        727
>                                                   F(  50,    676) =     368.73
>                                                   Prob > F        =     0.0000
>                                                   R-squared       =     0.9367
>                                                   Adj R-squared   =     0.9320
>                                                   Root MSE        =     0.1811
>
> ------------------------------
> ------------------------------------------------
>              |               Robust
>  LabnewLand3 |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
> -------------+----------------------------------------------------------------
>          tpr |  -.0752534    .030686    -2.45   0.014    -.1355048   -.0150021
>       eshare |  -.2042971   .0787484    -2.59   0.010     -.358918   -.0496762
>      avrentp |   2.59e-06   7.47e-06     0.35   0.729    -.0000121    .0000173
>    sharecrop |   .1223223   .0690329     1.77   0.077    -.0132225    .2578671
>       tenant |   .1070509   .1124441     0.95   0.341    -.1137308    .3278327
>    nonagremp |  -.0185542   .0009113   -20.36   0.000    -.0203435   -.0167649
>   wheatshare |   .2611341   .0944493     2.76   0.006     .0756848    .4465834
>   wheatyield |   .0077474   .0026325     2.94   0.003     .0025786    .0129162
> piemonteva~a |   .1687091   .0581959     2.90   0.004     .0544426    .2829756
>      liguria |   .1656128   .0810158     2.04   0.041     .0065398    .3246857
>    lombardia |    .051234   .0601551     0.85   0.395    -.0668793    .1693473
> trentinoal~e |   .1392318   .0809547     1.72   0.086     -.019721    .2981846
>       veneto |  -.0195738   .0605925    -0.32   0.747    -.1385459    .0993983
>       emilia |  -.0295481   .0423374    -0.70   0.485    -.1126767    .0535805
>      toscana |   .0268248   .0436844     0.61   0.539    -.0589485    .1125982
>        lazio |   .0405166   .0498447     0.81   0.417    -.0573524    .1383856
>      abruzzi |  -.1850101   .0471699    -3.92   0.000    -.2776273   -.0923929
>     campania |   -.007703   .0852096    -0.09   0.928    -.1750103    .1596043
>       puglie |  -.2555594   .0761643    -3.36   0.001    -.4051065   -.1060124
>      lucania |  -.1024758   .0858727    -1.19   0.233    -.2710851    .0661336
>     calabria |  -.2699014   .0986603    -2.74   0.006    -.4636189    -.076184
>      sicilia |  -.4293593   .1652127    -2.60   0.010     -.753751   -.1049676
>     sardegna |  -.4646977   .0892632    -5.21   0.000    -.6399643   -.2894312
>      avmrain |  -.0081846   .0161084    -0.51   0.612    -.0398132     .023444
>    cvavmrain |   .0811425    .192954     0.42   0.674    -.2977187    .4600036
>      rainwin |   .0013707    .001745     0.79   0.432    -.0020556     .004797
>      rainspr |  -.0015337   .0015158    -1.01   0.312      -.00451    .0014426
>      rainsum |    .001587   .0014179     1.12   0.263    -.0011969     .004371
>      rainaut |   .0022904   .0014189     1.61   0.107    -.0004955    .0050763
>     rainwin2 |   1.97e-07   8.11e-07     0.24   0.808    -1.40e-06    1.79e-06
>     rainspr2 |   1.39e-06   5.14e-07     2.71   0.007     3.83e-07    2.40e-06
>     rainsum2 |  -2.37e-07   6.17e-07    -0.38   0.701    -1.45e-06    9.75e-07
>     rainaut2 |  -2.03e-06   8.34e-07    -2.43   0.015    -3.67e-06   -3.93e-07
>    cvrainwin |  -.1337135   .0910987    -1.47   0.143    -.3125838    .0451569
>    cvrainspr |  -.0919449   .1411574    -0.65   0.515    -.3691047    .1852148
>    cvrainsum |   .0620552   .0583617     1.06   0.288    -.0525368    .1766472
>    cvrainaut |  -.0228216   .1275591    -0.18   0.858    -.2732812     .227638
>   rainintwin |  -.0038742     .01052    -0.37   0.713      -.02453    .0167816
>   rainintspr |    .025346   .0082647     3.07   0.002     .0091184    .0415735
>   rainintsum |  -.0158319   .0053415    -2.96   0.003    -.0263199   -.0053438
>   rainintaut |  -.0026335    .008307    -0.32   0.751    -.0189442    .0136772
> cvrainintwin |   .1142515   .1082358     1.06   0.292    -.0982673    .3267703
> cvrainintspr |  -.1338668    .071614    -1.87   0.062    -.2744795    .0067459
> cvrainintsum |  -.0174779   .0458837    -0.38   0.703    -.1075696    .0726138
> cvrainintaut |   -.047752   .0917345    -0.52   0.603    -.2278708    .1323668
>      height1 |  -.0000976   .0000593    -1.65   0.100    -.0002141    .0000189
>   dislivello |  -.0001469   .0001313    -1.12   0.263    -.0004047    .0001108
>     newslope |   36.73272   10.35384     3.55   0.000     16.40318    57.06227
>     latitude |   .0000167   .0002471     0.07   0.946    -.0004684    .0005018
>  lnpop31land |   .8216411   .0354665    23.17   0.000     .7520034    .8912789
>        _cons |  -.5036778     1.1633    -0.43   0.665    -2.787793    1.780437
> ------------------------------------------------------------------------------
>
>
> Instrumental variables (GMM) regression                Number of obs =     727
>                                                        Wald chi2(50) = 7531.25
>                                                        Prob > chi2   =  0.0000
>                                                        R-squared     =  0.8935
> GMM weight matrix: Robust                              Root MSE      =  .31984
>
> ------------------------------------------------------------------------------
>              |               Robust
>    lnrtw240w |      Coef.   Std. Err.      z    P>|z|     [95% Conf. Interval]
> -------------+----------------------------------------------------------------
>  LabnewLand3 |   .7296731   .0479797    15.21   0.000     .6356347    .8237115
>          tpr |    .150806   .0322902     4.67   0.000     .0875184    .2140937
>       eshare |  -.5659457   .1465112    -3.86   0.000    -.8531023   -.2787891
>      avrentp |   .0001132   .0000133     8.51   0.000     .0000871    .0001393
>    sharecrop |  -.3001512   .1163504    -2.58   0.010    -.5281938   -.0721086
>       tenant |  -.0879874   .1825934    -0.48   0.630     -.445864    .2698891
>    nonagremp |   .0044146   .0009902     4.46   0.000     .0024738    .0063554
>   wheatshare |   .2725696   .1986782     1.37   0.170    -.1168325    .6619717
>   wheatyield |    .013572   .0048236     2.81   0.005     .0041179     .023026
> piemonteva~a |   .3870626   .1211705     3.19   0.001     .1495729    .6245524
>      liguria |  -.7231312   .1708928    -4.23   0.000    -1.058075   -.3881875
>    lombardia |   .0804358    .125656     0.64   0.522    -.1658454     .326717
> trentinoal~e |   .4460556   .1907816     2.34   0.019     .0721305    .8199806
>       veneto |    .200405   .1249244     1.60   0.109    -.0444424    .4452523
>       emilia |  -.1549017    .080782    -1.92   0.055    -.3132315    .0034282
>      toscana |  -.2256237   .0731365    -3.08   0.002    -.3689686   -.0822789
>        lazio |   .2176652   .0838542     2.60   0.009      .053314    .3820164
>      abruzzi |   .4261649   .0839904     5.07   0.000     .2615467     .590783
>     campania |   .5052329   .1338471     3.77   0.000     .2428974    .7675684
>       puglie |   .7343379   .1313001     5.59   0.000     .4769945    .9916814
>      lucania |   .1794245   .1634261     1.10   0.272    -.1408848    .4997337
>     calabria |   .2868967   .1928984     1.49   0.137    -.0911772    .6649707
>      sicilia |   .4136089   .3124951     1.32   0.186    -.1988704    1.026088
>     sardegna |  -.1242169   .1713119    -0.73   0.468     -.459982    .2115482
>      avmrain |   .0922622   .0298397     3.09   0.002     .0337775    .1507469
>    cvavmrain |   .1573777   .2786143     0.56   0.572    -.3886963    .7034517
>      rainwin |  -.0085693   .0028028    -3.06   0.002    -.0140627    -.003076
>      rainspr |    -.00659   .0028498    -2.31   0.021    -.0121755   -.0010046
>      rainsum |  -.0082152   .0027455    -2.99   0.003    -.0135962   -.0028343
>      rainaut |  -.0064073   .0027679    -2.31   0.021    -.0118322   -.0009823
>     rainwin2 |   7.00e-07   1.41e-06     0.50   0.619    -2.06e-06    3.46e-06
>     rainspr2 |  -1.61e-06   1.40e-06    -1.15   0.251    -4.35e-06    1.14e-06
>     rainsum2 |  -6.10e-07   1.36e-06    -0.45   0.653    -3.27e-06    2.05e-06
>     rainaut2 |  -1.55e-06   1.39e-06    -1.11   0.266    -4.28e-06    1.18e-06
>    cvrainwin |   .4861783   .1740445     2.79   0.005     .1450574    .8272992
>    cvrainspr |  -.2146707   .2086629    -1.03   0.304    -.6236425    .1943011
>    cvrainsum |  -.0934008   .1286739    -0.73   0.468     -.345597    .1587954
>    cvrainaut |  -.1363144   .2075616    -0.66   0.511    -.5431277    .2704988
>   rainintwin |  -.0395274   .0188358    -2.10   0.036    -.0764449     -.00261
>   rainintspr |   .0195541   .0182292     1.07   0.283    -.0161746    .0552827
>   rainintsum |  -.0010367   .0122977    -0.08   0.933    -.0251396    .0230663
>   rainintaut |   .0029407   .0158345     0.19   0.853    -.0280944    .0339758
> cvrainintwin |  -.2216308   .1662473    -1.33   0.182    -.5474696     .104208
> cvrainintspr |   .1727809    .142595     1.21   0.226    -.1067001    .4522619
> cvrainintsum |   .1093444   .0924789     1.18   0.237     -.071911    .2905998
> cvrainintaut |  -.0724951   .1695741    -0.43   0.669    -.4048543    .2598641
>      height1 |  -.0005161   .0001042    -4.95   0.000    -.0007204   -.0003118
>   dislivello |  -.0000686   .0002411    -0.28   0.776    -.0005412     .000404
>     newslope |  -4.832518   17.70387    -0.27   0.785    -39.53147    29.86644
>     latitude |   .0000422   .0004341     0.10   0.922    -.0008086    .0008931
>        _cons |  -2.906064   2.013513    -1.44   0.149    -6.852477    1.040349
> ------------------------------------------------------------------------------
> Instrumented:  LabnewLand3
> Instruments:   tpr eshare avrentp sharecrop tenant nonagremp wheatshare
>                wheatyield piemontevalledaosta liguria lombardia
>                trentinoaltoadige veneto emilia toscana lazio abruzzi
>                campania puglie lucania calabria sicilia sardegna avmrain
>                cvavmrain rainwin rainspr rainsum rainaut rainwin2 rainspr2
>                rainsum2 rainaut2 cvrainwin cvrainspr cvrainsum cvrainaut
>                rainintwin rainintspr rainintsum rainintaut cvrainintwin
>                cvrainintspr cvrainintsum cvrainintaut height1 dislivello
>                newslope latitude lnpop31land
>
> Additionally, at this point, I have another question. Does anyone know
> why the F-statistic is substituted for a Wald statistic in the second
> stage? If I adjust for small samples, I get again the F-statistic.
> However, I don't see why one should adjust for small amples with
> n=727...
>
> 2013/10/29 pablo martinelli <pab.martinelli@gmail.com>:
>> Hi everyone again.
>>
>> No, ivreg2 does not drop the constant.
>>
>> Yes, sure, Mark. Here are my command lines the results i get. Since I
>> have many variables, and tehre is a limit to the message's size we can
>> send, I will split them.
>>
>> First, ivregress.
>>
>> . ivregress 2sls lnrtw240w tpr eshare avrentp sharecrop tenant
>> nonagremp wheatshare wheatyield piemontevalledaosta liguria lombardia
>> trentinoaltoadige veneto emilia toscana lazio abruzzi campania pugli
>>> e lucania calabria sicilia sardegna avmrain cvavmrain rainwin rainspr rainsum rainaut rainwin2 rainspr2 rainsum2 rainaut2 cvrainwin cvrainspr cvrainsum cvrainaut rainintwin rainintspr rainintsum rain
>>> intaut cvrainintwin cvrainintspr cvrainintsum cvrainintaut height1 dislivello newslope latitude (LabnewLand3=lnpop31land), first robust
>>
>> First-stage regressions
>> -----------------------
>>
>>                                                   Number of obs   =        727
>>                                                   F(  50,    676) =     368.73
>>                                                   Prob > F        =     0.0000
>>                                                   R-squared       =     0.9367
>>                                                   Adj R-squared   =     0.9320
>>                                                   Root MSE        =     0.1811
>>
>> ------------------------------
>> ------------------------------------------------
>>              |               Robust
>>  LabnewLand3 |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
>> -------------+----------------------------------------------------------------
>>          tpr |  -.0752534    .030686    -2.45   0.014    -.1355048   -.0150021
>>       eshare |  -.2042971   .0787484    -2.59   0.010     -.358918   -.0496762
>>      avrentp |   2.59e-06   7.47e-06     0.35   0.729    -.0000121    .0000173
>>    sharecrop |   .1223223   .0690329     1.77   0.077    -.0132225    .2578671
>>       tenant |   .1070509   .1124441     0.95   0.341    -.1137308    .3278327
>>    nonagremp |  -.0185542   .0009113   -20.36   0.000    -.0203435   -.0167649
>>   wheatshare |   .2611341   .0944493     2.76   0.006     .0756848    .4465834
>>   wheatyield |   .0077474   .0026325     2.94   0.003     .0025786    .0129162
>> piemonteva~a |   .1687091   .0581959     2.90   0.004     .0544426    .2829756
>>      liguria |   .1656128   .0810158     2.04   0.041     .0065398    .3246857
>>    lombardia |    .051234   .0601551     0.85   0.395    -.0668793    .1693473
>> trentinoal~e |   .1392318   .0809547     1.72   0.086     -.019721    .2981846
>>       veneto |  -.0195738   .0605925    -0.32   0.747    -.1385459    .0993983
>>       emilia |  -.0295481   .0423374    -0.70   0.485    -.1126767    .0535805
>>      toscana |   .0268248   .0436844     0.61   0.539    -.0589485    .1125982
>>        lazio |   .0405166   .0498447     0.81   0.417    -.0573524    .1383856
>>      abruzzi |  -.1850101   .0471699    -3.92   0.000    -.2776273   -.0923929
>>     campania |   -.007703   .0852096    -0.09   0.928    -.1750103    .1596043
>>       puglie |  -.2555594   .0761643    -3.36   0.001    -.4051065   -.1060124
>>      lucania |  -.1024758   .0858727    -1.19   0.233    -.2710851    .0661336
>>     calabria |  -.2699014   .0986603    -2.74   0.006    -.4636189    -.076184
>>      sicilia |  -.4293593   .1652127    -2.60   0.010     -.753751   -.1049676
>>     sardegna |  -.4646977   .0892632    -5.21   0.000    -.6399643   -.2894312
>>      avmrain |  -.0081846   .0161084    -0.51   0.612    -.0398132     .023444
>>    cvavmrain |   .0811425    .192954     0.42   0.674    -.2977187    .4600036
>>      rainwin |   .0013707    .001745     0.79   0.432    -.0020556     .004797
>>      rainspr |  -.0015337   .0015158    -1.01   0.312      -.00451    .0014426
>>      rainsum |    .001587   .0014179     1.12   0.263    -.0011969     .004371
>>      rainaut |   .0022904   .0014189     1.61   0.107    -.0004955    .0050763
>>     rainwin2 |   1.97e-07   8.11e-07     0.24   0.808    -1.40e-06    1.79e-06
>>     rainspr2 |   1.39e-06   5.14e-07     2.71   0.007     3.83e-07    2.40e-06
>>     rainsum2 |  -2.37e-07   6.17e-07    -0.38   0.701    -1.45e-06    9.75e-07
>>     rainaut2 |  -2.03e-06   8.34e-07    -2.43   0.015    -3.67e-06   -3.93e-07
>>    cvrainwin |  -.1337135   .0910987    -1.47   0.143    -.3125838    .0451569
>>    cvrainspr |  -.0919449   .1411574    -0.65   0.515    -.3691047    .1852148
>>    cvrainsum |   .0620552   .0583617     1.06   0.288    -.0525368    .1766472
>>    cvrainaut |  -.0228216   .1275591    -0.18   0.858    -.2732812     .227638
>>   rainintwin |  -.0038742     .01052    -0.37   0.713      -.02453    .0167816
>>   rainintspr |    .025346   .0082647     3.07   0.002     .0091184    .0415735
>>   rainintsum |  -.0158319   .0053415    -2.96   0.003    -.0263199   -.0053438
>>   rainintaut |  -.0026335    .008307    -0.32   0.751    -.0189442    .0136772
>> cvrainintwin |   .1142515   .1082358     1.06   0.292    -.0982673    .3267703
>> cvrainintspr |  -.1338668    .071614    -1.87   0.062    -.2744795    .0067459
>> cvrainintsum |  -.0174779   .0458837    -0.38   0.703    -.1075696    .0726138
>> cvrainintaut |   -.047752   .0917345    -0.52   0.603    -.2278708    .1323668
>>      height1 |  -.0000976   .0000593    -1.65   0.100    -.0002141    .0000189
>>   dislivello |  -.0001469   .0001313    -1.12   0.263    -.0004047    .0001108
>>     newslope |   36.73272   10.35384     3.55   0.000     16.40318    57.06227
>>     latitude |   .0000167   .0002471     0.07   0.946    -.0004684    .0005018
>>  lnpop31land |   .8216411   .0354665    23.17   0.000     .7520034    .8912789
>>        _cons |  -.5036778     1.1633    -0.43   0.665    -2.787793    1.780437
>> ------------------------------------------------------------------------------
>>
>>
>> Instrumental variables (2SLS) regression               Number of obs =     727
>>                                                        Wald chi2(50) =20562.26
>>                                                        Prob > chi2   =  0.0000
>>                                                        R-squared     =  0.8932
>>                                                        Root MSE      =  .32042
>>
>> ------------------------------------------------------------------------------
>>              |               Robust
>>    lnrtw240w |      Coef.   Std. Err.      z    P>|z|     [95% Conf. Interval]
>> -------------+----------------------------------------------------------------
>>  LabnewLand3 |   .7267861   .0450934    16.12   0.000     .6384046    .8151675
>>          tpr |   .1458045    .032423     4.50   0.000     .0822565    .2093525
>>       eshare |  -.5817712   .1438029    -4.05   0.000    -.8636196   -.2999228
>>      avrentp |   .0001137   .0000132     8.63   0.000     .0000879    .0001395
>>    sharecrop |  -.2948938    .115277    -2.56   0.011    -.5208325   -.0689551
>>       tenant |  -.0748224   .1830473    -0.41   0.683    -.4335884    .2839437
>>    nonagremp |   .0045094   .0009825     4.59   0.000     .0025837    .0064351
>>   wheatshare |    .268118   .1990714     1.35   0.178    -.1220547    .6582907
>>   wheatyield |   .0150569   .0046811     3.22   0.001      .005882    .0242317
>> piemonteva~a |    .457105   .1139754     4.01   0.000     .2337173    .6804928
>>      liguria |  -.6659745   .1643922    -4.05   0.000    -.9881773   -.3437717
>>    lombardia |   .1699226   .1148089     1.48   0.139    -.0550987    .3949439
>> trentinoal~e |   .5750365   .1708428     3.37   0.001     .2401908    .9098822
>>       veneto |   .3072996   .1069846     2.87   0.004     .0976137    .5169855
>>       emilia |  -.0965144   .0759654    -1.27   0.204    -.2454038     .052375
>>      toscana |  -.2014353    .068682    -2.93   0.003    -.3360495   -.0668211
>>        lazio |   .1704884   .0814061     2.09   0.036     .0109354    .3300414
>>      abruzzi |   .3654339   .0807196     4.53   0.000     .2072264    .5236413
>>     campania |     .38231   .1131769     3.38   0.001     .1604874    .6041327
>>       puglie |   .6174175   .1138966     5.42   0.000     .3941843    .8406508
>>      lucania |   .0233558   .1259724     0.19   0.853    -.2235455    .2702572
>>     calabria |   .0643192   .1278942     0.50   0.615    -.1863488    .3149872
>>      sicilia |   .0892816   .1851743     0.48   0.630    -.2736534    .4522166
>>     sardegna |  -.2924706   .1315056    -2.22   0.026    -.5502168   -.0347244
>>      avmrain |    .091309   .0299047     3.05   0.002     .0326968    .1499212
>>    cvavmrain |   .0704218   .2632369     0.27   0.789    -.4455132    .5863567
>>      rainwin |  -.0085437   .0027881    -3.06   0.002    -.0140082   -.0030791
>>      rainspr |  -.0065773   .0028433    -2.31   0.021      -.01215   -.0010046
>>      rainsum |  -.0078591   .0027321    -2.88   0.004     -.013214   -.0025043
>>      rainaut |  -.0064453   .0027802    -2.32   0.020    -.0118943   -.0009963
>>     rainwin2 |   8.42e-07   1.35e-06     0.62   0.534    -1.81e-06    3.50e-06
>>     rainspr2 |  -1.64e-06   1.41e-06    -1.17   0.244    -4.40e-06    1.12e-06
>>     rainsum2 |  -7.44e-07   1.30e-06    -0.57   0.568    -3.30e-06    1.81e-06
>>     rainaut2 |  -1.36e-06   1.39e-06    -0.98   0.328    -4.08e-06    1.36e-06
>>    cvrainwin |   .5463342   .1663811     3.28   0.001     .2202332    .8724353
>>    cvrainspr |  -.1413404   .1943371    -0.73   0.467    -.5222341    .2395533
>>    cvrainsum |  -.0781232   .1270969    -0.61   0.539    -.3272285    .1709822
>>    cvrainaut |  -.1209869    .209468    -0.58   0.564    -.5315367    .2895629
>>   rainintwin |  -.0434683   .0193887    -2.24   0.025    -.0814695   -.0054672
>>   rainintspr |   .0229036   .0185125     1.24   0.216    -.0133803    .0591875
>>   rainintsum |     -.0028   .0119597    -0.23   0.815    -.0262406    .0206406
>>   rainintaut |   .0026536   .0160065     0.17   0.868    -.0287186    .0340258
>> cvrainintwin |  -.1953799   .1654534    -1.18   0.238    -.5196627    .1289029
>> cvrainintspr |   .1423667   .1475175     0.97   0.335    -.1467623    .4314956
>> cvrainintsum |   .0937196   .0911865     1.03   0.304    -.0850026    .2724418
>> cvrainintaut |   -.072203   .1696257    -0.43   0.670    -.4046632    .2602572
>>      height1 |   -.000493   .0001032    -4.78   0.000    -.0006953   -.0002908
>>   dislivello |  -.0001017     .00021    -0.48   0.628    -.0005132    .0003099
>>     newslope |          0   .0039293     0.00   1.000    -.0077012    .0077012
>>     latitude |  -.0005574    .000063    -8.85   0.000    -.0006808   -.0004339
>>        _cons |  (omitted)
>> ------------------------------------------------------------------------------
>> Instrumented:  LabnewLand3
>> Instruments:   tpr eshare avrentp sharecrop tenant nonagremp wheatshare
>>                wheatyield piemontevalledaosta liguria lombardia
>>                trentinoaltoadige veneto emilia toscana lazio abruzzi
>>                campania puglie lucania calabria sicilia sardegna avmrain
>>                cvavmrain rainwin rainspr rainsum rainaut rainwin2 rainspr2
>>                rainsum2 rainaut2 cvrainwin cvrainspr cvrainsum cvrainaut
>>                rainintwin rainintspr rainintsum rainintaut cvrainintwin
>>                cvrainintspr cvrainintsum cvrainintaut height1 dislivello
>>                newslope latitude lnpop31land
>>
>> I know, scaling might be a problem. In particular, if I multiply all
>> the values of the variable newslope for 100 or 1000, I get a
>> coefficient that is not 0 and a p-value that is not 1 (though is not
>> statistically significant). Everything else, remains the same. So the
>> problem is not  lack of variation in newslope, as one may be tempted
>> to think having a look at the results just above. However, the
>> omission of the variable happens only when the 3 variables height1,
>> dislivello and newslope (which are correlated) are entered as
>> regressors, although I am not able to conceptually find the reason for
>> the constant being dropped.
>>
>> 2013/10/28 Schaffer, Mark E <M.E.Schaffer@hw.ac.uk>:
>>> Pablo,
>>>
>>> You need to give us more details, such as the command lines used.  Also, you say
>>>
>>>> A potential explanation is that the original ivreg code estimated IV by default
>>>> with gmm
>>>
>>> but that's impossible, because Stata's official -ivreg- never implemented GMM.
>>>
>>> Does -ivreg2- with and without -gmm2s- keep or drop the constant?
>>>
>>> --Mark
>>>
>>>> -----Original Message-----
>>>> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-
>>>> statalist@hsphsun2.harvard.edu] On Behalf Of pablo martinelli
>>>> Sent: 28 October 2013 15:22
>>>> To: statalist@hsphsun2.harvard.edu
>>>> Subject: st: omitted constant with ivregress 2sls but not with ivregress gmm or
>>>> ivreg
>>>>
>>>> Hi all,
>>>> I am having some difficulties for replicating some results I get in 2011 with an
>>>> earlier version of Stata (I think it was Stata 7 but I am not sure). Now I am using
>>>> Stata 11.
>>>> The problem is the following.
>>>> When I use ivregress 2sls, Stata omits the constant, even though it is not
>>>> perfectly collinear with any exogenous or endogenous variables. The
>>>> coefficients are slightly modified with respect to the original results.
>>>> (the problem doesn't happen when I use ols).
>>>> If I use ivregress gmm with robust standard errors I get the original resulst I get
>>>> in 2011, except for the constant whose estimated value is somewhat different
>>>> from the orginal. F-statistics, R2, etc are also the same. I obtain the same
>>>> results with either ivreg and ivreg2.
>>>> A potential explanation is that the original ivreg code estimated IV by default
>>>> with gmm, though I have not been able to find confirmation of this point.
>>>> Some of the regressors are certainly correlated, but not perfectly.
>>>> Anyway, I cannot figure out why should the constant be ommited with ivregress
>>>> 2sls and not with ivregress gmm. What is the econometric problem here? And
>>>> why should in that case any of the two methods (2sls or gmm) preferable to the
>>>> other?
>>>> Any explanation, suggestion or hint would be highly appreciated.
>>>> Best,
>>>> Pablo Martinelli
>>>> *
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>>>> *   http://www.ats.ucla.edu/stat/stata/
>>>
>>>
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