Hello,

my data: panel data, 260 observations; 20 Regions and time period: 2004 to 2016.

I have found endogeneity between corruption and GDP growth and I have chosen FE over RE because of the results of the Hausman test. Also, I chose LSDV over FE-2SLS because I would like to see the dummy coefficients.

Hence, I am running a LSDV model where I want to see the effect that the Corruption level (coded as Cor) of each Region(coded as countrynum) has on Y(which is GDP growth rate).

I do not understand why the model is significant with i.countrynum, but it becomes insignificant when I include i.Year. Also, when using i.countrynum, why would my variable of corruption become insignificant when I use log(corruption) instead of Corruption?

Also, I have run testparm on i.countrynum and i.year and the p values are close to 0.

Code:
 . reg  Y I logYlevel_1 n H Cor i.countrynum, robust

Linear regression                               Number of obs     =        240
                                                F(24, 215)        =       4.04
                                                Prob > F          =     0.0000
                                                R-squared         =     0.2233
                                                Root MSE          =     .02424

------------------------------------------------------------------------------
             |               Robust
           Y |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
           I |   .0421328   .0235268     1.79   0.075      -.00424    .0885055
 logYlevel_1 |  -.2725869   .0477639    -5.71   0.000    -.3667323   -.1784415
           n |  -.0011075   .0002068    -5.36   0.000    -.0015151      -.0007
           H |  -.5249337   .1279176    -4.10   0.000     -.777067   -.2728005
         Cor |   152.1827     43.705     3.48   0.001     66.03756    238.3279
             |
  countrynum |
          2  |  -.0568746    .018295    -3.11   0.002     -.092935   -.0208142
          3  |  -.1177966   .0196517    -5.99   0.000    -.1565313    -.079062
          4  |   -.132077   .0269762    -4.90   0.000    -.1852487   -.0789053
          5  |   .0762482   .0194006     3.93   0.000     .0380084    .1144879
          6  |   .0528407   .0149889     3.53   0.001     .0232966    .0823847
          7  |   .0857303   .0238629     3.59   0.000     .0386951    .1327655
          8  |   .0685547   .0154954     4.42   0.000     .0380124     .099097
          9  |   .0485808   .0342438     1.42   0.157    -.0189157    .1160773
         10  |   .0277995     .01135     2.45   0.015     .0054279    .0501711
         11  |  -.0446546   .0128474    -3.48   0.001    -.0699775   -.0193316
         12  |   .0164898   .0176551     0.93   0.351    -.0183094     .051289
         13  |   -.129616   .0228253    -5.68   0.000    -.1746061    -.084626
         14  |  -.0697799   .0127563    -5.47   0.000    -.0949234   -.0446365
         15  |  -.1306724   .0235665    -5.54   0.000    -.1771235   -.0842214
         16  |   .0428457   .0137236     3.12   0.002     .0157956    .0698958
         17  |   .1167549    .021726     5.37   0.000     .0739316    .1595782
         18  |   .0173388   .0115789     1.50   0.136    -.0054839    .0401616
         19  |   .0970503   .0240081     4.04   0.000     .0497288    .1443717
         20  |   .0306902   .0163222     1.88   0.061    -.0014819    .0628623
             |
       _cons |   2.812614   .4884072     5.76   0.000     1.849934    3.775293
------------------------------------------------------------------------------
Code:
. reg  Y I logYlevel_1 n H logCor i.countrynum,robust

Linear regression                               Number of obs     =        225
                                                F(24, 200)        =       4.83
                                                Prob > F          =     0.0000
                                                R-squared         =     0.2391
                                                Root MSE          =      .0232

------------------------------------------------------------------------------
             |               Robust
           Y |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
           I |   .0438102    .023208     1.89   0.061    -.0019535    .0895738
 logYlevel_1 |  -.2952572   .0474944    -6.22   0.000    -.3889112   -.2016031
           n |  -.0010141   .0001769    -5.73   0.000     -.001363   -.0006652
           H |  -.5967442   .1222761    -4.88   0.000      -.83786   -.3556284
      logCor |  -.0001871    .002452    -0.08   0.939    -.0050222     .004648
             |
  countrynum |
          2  |  -.0776557   .0163377    -4.75   0.000     -.109872   -.0454395
          3  |  -.1267072   .0195275    -6.49   0.000    -.1652135   -.0882009
          4  |  -.1387356   .0270324    -5.13   0.000    -.1920407   -.0854305
          5  |   .0833008   .0189025     4.41   0.000      .046027    .1205746
          6  |   .0572389   .0149254     3.83   0.000     .0278075    .0866703
          7  |   .0958031   .0238787     4.01   0.000     .0487167    .1428895
          8  |   .0765805   .0158141     4.84   0.000     .0453967    .1077642
          9  |   .0565331   .0340127     1.66   0.098    -.0105365    .1236026
         10  |    .030444    .011336     2.69   0.008     .0080905    .0527975
         11  |  -.0304818   .0129706    -2.35   0.020    -.0560585   -.0049051
         12  |   .0196087   .0175451     1.12   0.265    -.0149885    .0542058
         13  |   -.139783   .0227806    -6.14   0.000    -.1847039   -.0948621
         14  |  -.0761153   .0127299    -5.98   0.000    -.1012175   -.0510132
         15  |  -.1402884   .0235798    -5.95   0.000    -.1867854   -.0937915
         16  |   .0473936   .0139128     3.41   0.001      .019959    .0748281
         17  |   .1254732    .021914     5.73   0.000      .082261    .1686854
         18  |   .0189846   .0122194     1.55   0.122    -.0051108    .0430799
         19  |   .1095675   .0269841     4.06   0.000     .0563576    .1627774
         20  |   .0338714   .0162419     2.09   0.038     .0018441    .0658987
             |
       _cons |   3.049778   .4834469     6.31   0.000     2.096471    4.003085
------------------------------------------------------------------------------
Code:
. reg  Y I logYlevel_1 n H Cor i.countrynum i.Year, robust

Linear regression                               Number of obs     =        240
                                                F(35, 204)        =      19.07
                                                Prob > F          =     0.0000
                                                R-squared         =     0.7447
                                                Root MSE          =     .01427

------------------------------------------------------------------------------
             |               Robust
           Y |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
           I |  -.0017374   .0152018    -0.11   0.909    -.0317101    .0282353
 logYlevel_1 |  -.1344197    .043968    -3.06   0.003    -.2211097   -.0477297
           n |  -.0000933   .0003057    -0.31   0.761    -.0006961    .0005095
           H |   .1089849   .1461164     0.75   0.457     -.179107    .3970768
         Cor |   42.22968   27.68753     1.53   0.129    -12.36074    96.82009
             |
  countrynum |
          2  |  -.0151863   .0160518    -0.95   0.345     -.046835    .0164625
          3  |  -.0482293   .0157838    -3.06   0.003    -.0793496    -.017109
          4  |  -.0381451   .0174077    -2.19   0.030    -.0724672    -.003823
          5  |   .0448873   .0187381     2.40   0.018     .0079421    .0818325
          6  |   .0300398   .0107687     2.79   0.006     .0088075    .0512721
          7  |   .0336804   .0214411     1.57   0.118    -.0085941     .075955
          8  |   .0259668    .011634     2.23   0.027     .0030284    .0489052
          9  |   .0567836   .0316731     1.79   0.074     -.005665    .1192323
         10  |   .0101893   .0064318     1.58   0.115    -.0024919    .0228706
         11  |  -.0263025   .0101509    -2.59   0.010    -.0463165   -.0062884
         12  |   .0268867   .0158145     1.70   0.091    -.0042941    .0580675
         13  |  -.0394516   .0159554    -2.47   0.014    -.0709102    -.007993
         14  |  -.0212305   .0097003    -2.19   0.030    -.0403562   -.0021048
         15  |  -.0406477   .0160236    -2.54   0.012    -.0722408   -.0090546
         16  |    .026545   .0117709     2.26   0.025     .0033367    .0497533
         17  |   .0621137   .0196756     3.16   0.002       .02332    .1009073
         18  |  -.0060011   .0064424    -0.93   0.353    -.0187033     .006701
         19  |    .049247   .0188249     2.62   0.010     .0121307    .0863634
         20  |   .0361759   .0169272     2.14   0.034     .0028012    .0695507
             |
        Year |
       2006  |   .0145628   .0034744     4.19   0.000     .0077125    .0214131
       2007  |   .0062804   .0040101     1.57   0.119    -.0016263     .014187
       2008  |  -.0235486    .005161    -4.56   0.000    -.0337243    -.013373
       2009  |  -.0631985   .0054573   -11.58   0.000    -.0739584   -.0524386
       2010  |  -.0056302   .0071231    -0.79   0.430    -.0196746    .0084142
       2011  |  -.0116207   .0053297    -2.18   0.030     -.022129   -.0011123
       2012  |  -.0420052    .006943    -6.05   0.000    -.0556944   -.0283159
       2013  |  -.0412766   .0104555    -3.95   0.000    -.0618912   -.0206619
       2014  |  -.0257527   .0091024    -2.83   0.005    -.0436995   -.0078059
       2015  |  -.0074938   .0120268    -0.62   0.534    -.0312067    .0162191
       2016  |  -.0120389   .0093528    -1.29   0.199    -.0304795    .0064017
             |
       _cons |   1.349846   .4464339     3.02   0.003     .4696303    2.230063
------------------------------------------------------------------------------
Code:
 reg  Y I logYlevel_1 n H Cor  i.Year, robust

Linear regression                               Number of obs     =        240
                                                F(16, 223)        =      36.46
                                                Prob > F          =     0.0000
                                                R-squared         =     0.7030
                                                Root MSE          =     .01472

------------------------------------------------------------------------------
             |               Robust
           Y |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
           I |   .0002541   .0022204     0.11   0.909    -.0041216    .0046298
 logYlevel_1 |   .0047408   .0051855     0.91   0.362    -.0054781    .0149596
           n |  -.0002482   .0002666    -0.93   0.353    -.0007736    .0002772
           H |  -.0516428   .0513114    -1.01   0.315    -.1527602    .0494745
         Cor |   .9710216   20.83673     0.05   0.963    -40.09107    42.03312
             |
        Year |
       2006  |   .0150445   .0029372     5.12   0.000     .0092562    .0208328
       2007  |   .0066831   .0030496     2.19   0.029     .0006734    .0126929
       2008  |  -.0241049   .0040395    -5.97   0.000    -.0320654   -.0161444
       2009  |  -.0608203   .0044387   -13.70   0.000    -.0695674   -.0520731
       2010  |   .0056591   .0052307     1.08   0.280    -.0046489    .0159672
       2011  |  -.0011653   .0038145    -0.31   0.760    -.0086823    .0063518
       2012  |  -.0292677   .0043704    -6.70   0.000    -.0378802   -.0206552
       2013  |  -.0219385   .0081194    -2.70   0.007     -.037939    -.005938
       2014  |  -.0047909   .0041872    -1.14   0.254    -.0130425    .0034608
       2015  |   .0144844   .0063197     2.29   0.023     .0020304    .0269385
       2016  |   .0083592   .0044414     1.88   0.061    -.0003933    .0171117
             |
       _cons |  -.0385648   .0492351    -0.78   0.434    -.1355904    .0584608
------------------------------------------------------------------------------