Hello,

My sample is 27 countries over the period 1970-2020.

Code:
* Example generated by -dataex-. For more info, type help dataex
clear
input float(ln_co2pc_gr res_share_ch ei_ch) long pais float year
           .          .             . 1 1970
   .04318523  -.6838717  8.359551e-06 1 1971
 -.003316879  -.5843963   .0009368509 1 1972
  .035467148 -.19065896   .0010287017 1 1973
  -.01744461  1.1816183  -.0017663687 1 1974
  -.04150105 -1.1635613  -.0006288141 1 1975
   .02756405  -.4502255    .004128687 1 1976
     .027318   .4519265   -.003269479 1 1977
  -.01889515   .7232267    .005923823 1 1978
   .03856087 -.03159031   -.003776513 1 1979
 -.033974648  1.6892276 .000064082444 1 1980
  -.03340912   .3562208    .003573708 1 1981
 -.029852867     .22335   .0005264431 1 1982
  .010718346  .55891395  -.0008517876 1 1983
 -.025982857   .3025955   .0005473718 1 1984
  -.09177828   .2845615    .001306817 1 1985
   .06215334 -.57471985  -.0015678406 1 1986
  .035816193 -.04727695   .0022074506 1 1987
   .01995754 -2.0891473   .0035996065 1 1988
    -.051548  -.8556552    .003797956 1 1989
  -.08002138  2.5997005 -.00005368143 1 1990
   .04825544  -.7621235  -.0037634596 1 1991
  .014944077   .8977495   -.004395187 1 1992
  .020612717   .9866562   -.005773418 1 1993
   .02478409  .05130513  .00046010315 1 1994
 -.012306213   .1040608     .00382334 1 1995
   .04091835   -.889446  -.0021086782 1 1996
 .0079956055   .5504242  -.0032310635 1 1997
  .014033318  .14474016  -.0015993714 1 1998
  .029364586 -1.4123623    .004682116 1 1999
 -.013619423  -.7077209     .00665576 1 2000
  -.04242325  1.7975198  -.0001920089 1 2001
 -.064777374   .4461319    .007865772 1 2002
   .05957603  -.9268353   -.001951866 1 2003
   .07559109 -1.3884256  .00006687641 1 2004
   .02943516  .53251714   -.005813979 1 2005
   .04256248  .10701164   -.003355786 1 2006
   .08056164 -1.0392638  -.0004028007 1 2007
   .02333355   .4650531  -.0015919358 1 2008
  -.07792091  1.7649453   -.000819169 1 2009
   .07104397   .3953756   -.003054425 1 2010
  .036629677  .19075124  -.0014053434 1 2011
  .005539894  -.5361876     .00164406 1 2012
  .017653465 .006848871  .00021656603 1 2013
  -.02623844   .9186995   .0021337345 1 2014
   .01380539 -1.0696038  -.0012462884 1 2015
 -.014710426   .5231693   .0019309297 1 2016
 -.024267197  1.1013072  -.0033791065 1 2017
  -.04940796  -.1671047   .0008261427 1 2018
  -.03939629  -.0826373   .0004553869 1 2019
  -.12809563          .             . 1 2020
           .          .             . 2 1970
   .03735685  -3.583941             . 2 1971
  .006715775  -3.595976             . 2 1972
    .0723815  1.0047908             . 2 1973
 -.013946533  -2.443425             . 2 1974
   .06486988  -5.076143   .0021264479 2 1975
   .06060696   1.480327  -.0028430596 2 1976
   .15053034  -.9558575    .017706402 2 1977
   .05724525   -5.38981   -.004387319 2 1978
    .2042713  1.2600955    .011719197 2 1979
  .064723015   2.294343   -.007564358 2 1980
 .0004091263 -4.1512866     .00523252 2 1981
 -.010876656  -1.286386   .0008103475 2 1982
  -.08180618  -.2205604   -.015049823 2 1983
   .02359295  .52316314     .00834471 2 1984
  -.05776501  -.6478212   -.005634196 2 1985
     .281785  -.4750064     .02013827 2 1986
  .062625885  -5.436717   -.005898573 2 1987
  .008115768   .7065676   -.003384814 2 1988
   .05866051 -1.0042635    .006946467 2 1989
  -.02052593   .9601043   .0005567968 2 1990
-.0022001266   -.832518    .016187295 2 1991
  -.12391949  -1.431724    -.02331887 2 1992
 -.013767242  -1.408625    .002412543 2 1993
    .1101904   1.988639    .008190632 2 1994
  .034041405 -1.8642867    .006239846 2 1995
    .0448246   .2397784   .0004650354 2 1996
   .12469387  -.6353271    .007994488 2 1997
  -.02123642  .59386986  -.0091282725 2 1998
   .05735397   -2.49613   .0045640916 2 1999
   .04701233   2.706013     .00487949 2 2000
  -.04536247 -1.0512298   -.005044684 2 2001
 -.015072823  .05328191  -.0028871745 2 2002
 .0005598068 -.10914221  -.0025393665 2 2003
  .012296677  -.2341628 -.00010548532 2 2004
  .017718315   .7751106   -.003184572 2 2005
  .008773804 -1.2377497   -.007161543 2 2006
  .010412216   .3962357 -.00034835935 2 2007
   .15820885   -.927561     .01863219 2 2008
 -.035902023   .4229553   .0033046156 2 2009
  -.07738018  -.8142483   -.008181274 2 2010
    .0507679  -.3567042    .007837012 2 2011
  -.06547451 -.08397305   -.008323476 2 2012
  .010436058  -1.083137   .0025542825 2 2013
  -.09462738  .20679207   -.014072418 2 2014
 -.010979652 -1.1899234   -.004809044 2 2015
  -.06432438   .5234437   -.009212226 2 2016
  .026329994   .5948993    .004054792 2 2017
   .01234913   .7516962   .0006327629 2 2018
end
label values pais pais
label def pais 1 "Argentina", modify
label def pais 2 "Barbados", modify
I would like to explain the growth in per capita CO2 emissions (ln_co2pc_gr) by one-year lagged level of per capita CO2 emissions (l.ln_co2pc_gr), the growth in per capita GDP (ln_gdppc_gr), changes in Energy Intensity (ei_ch.), and the change of the renewable share into the primary energy supply (res_share_ch).

I have to compare results when:
  1. country and year fixed effects are omitted
  2. year fixed effects are omitted and country effects are added
  3. year fixed effects and country effects are added
I do the following:

Case 1. country and year fixed effects are omitted

Code:
. reg ln_co2pc_gr l.ln_co2pc res_share_ch ei_ch

      Source |       SS           df       MS      Number of obs   =     1,173
-------------+----------------------------------   F(3, 1169)      =    204.16
       Model |  4.37886025         3  1.45962008   Prob > F        =    0.0000
    Residual |  8.35748358     1,169  .007149259   R-squared       =    0.3438
-------------+----------------------------------   Adj R-squared   =    0.3421
       Total |  12.7363438     1,172  .010867188   Root MSE        =    .08455

------------------------------------------------------------------------------
 ln_co2pc_gr | Coefficient  Std. err.      t    P>|t|     [95% conf. interval]
-------------+----------------------------------------------------------------
    ln_co2pc |
         L1. |  -.0050447   .0027289    -1.85   0.065    -.0103987    .0003094
             |
res_share_ch |  -.0207655   .0009512   -21.83   0.000    -.0226317   -.0188993
       ei_ch |   2.793124   .2764864    10.10   0.000     2.250659    3.335589
       _cons |    .048808   .0200982     2.43   0.015     .0093755    .0882406
------------------------------------------------------------------------------
Case 2. year fixed effects are omitted and country effects are added.

Code:
. xtabond ln_co2pc_gr ln_gdppc_gr ei_ch res_share_ch, noconst

Arellano–Bond dynamic panel-data estimation     Number of obs     =      1,126
Group variable: pais                            Number of groups  =         25
Time variable: year
                                                Obs per group:
                                                              min =         17
                                                              avg =      45.04
                                                              max =         47

Number of instruments =    862                  Wald chi2(4)      =     968.45
                                                Prob > chi2       =     0.0000
One-step results
------------------------------------------------------------------------------
 ln_co2pc_gr | Coefficient  Std. err.      z    P>|z|     [95% conf. interval]
-------------+----------------------------------------------------------------
 ln_co2pc_gr |
         L1. |  -.1543293   .0217159    -7.11   0.000    -.1968917   -.1117669
             |
 ln_gdppc_gr |   1.141223   .0654731    17.43   0.000     1.012898    1.269548
       ei_ch |   3.959746    .279658    14.16   0.000     3.411626    4.507865
res_share_ch |  -.0172658   .0009338   -18.49   0.000     -.019096   -.0154355
------------------------------------------------------------------------------
Instruments for differenced equation
        GMM-type: L(2/.).ln_co2pc_gr
        Standard: D.ln_gdppc_gr D.ei_ch D.res_share_ch
Case 3. year fixed effects and country effects are added

Code:
. xtabond ln_co2pc_gr ln_gdppc_gr ei_ch res_share_ch yr*, noconst
note: yr1 omitted from div() because of collinearity.
note: yr2 omitted from div() because of collinearity.
note: yr51 omitted from div() because of collinearity.
note: yr1 omitted because of collinearity.
note: yr2 omitted because of collinearity.
note: yr51 omitted because of collinearity.

Arellano–Bond dynamic panel-data estimation     Number of obs     =      1,126
Group variable: pais                            Number of groups  =         25
Time variable: year
                                                Obs per group:
                                                              min =         17
                                                              avg =      45.04
                                                              max =         47

Number of instruments =    885                  Wald chi2(51)     =    1077.88
                                                Prob > chi2       =     0.0000
One-step results
------------------------------------------------------------------------------
 ln_co2pc_gr | Coefficient  Std. err.      z    P>|z|     [95% conf. interval]
-------------+----------------------------------------------------------------
 ln_co2pc_gr |
         L1. |  -.1699338   .0221739    -7.66   0.000    -.2133939   -.1264737
             |
 ln_gdppc_gr |   1.189569   .0714606    16.65   0.000     1.049509    1.329629
       ei_ch |   3.926077   .2800375    14.02   0.000     3.377213     4.47494
res_share_ch |  -.0164984   .0009514   -17.34   0.000    -.0183632   -.0146337
         yr3 |   .0086196   .0232371     0.37   0.711    -.0369241    .0541634
         yr4 |          0  (omitted)
         yr5 |  -.0095069    .023281    -0.41   0.683    -.0551368    .0361231
         yr6 |   .0047888   .0233236     0.21   0.837    -.0409246    .0505023
         yr7 |   .0116231   .0232843     0.50   0.618    -.0340132    .0572594
         yr8 |   .0150959   .0232158     0.65   0.516    -.0304061     .060598
         yr9 |   .0164546   .0232008     0.71   0.478    -.0290182    .0619273
        yr10 |  -.0110719   .0232537    -0.48   0.634    -.0566484    .0345045
        yr11 |  -.0092358    .023345    -0.40   0.692    -.0549912    .0365195
        yr12 |  -.0186959   .0233934    -0.80   0.424    -.0645461    .0271544
        yr13 |   .0080493   .0237823     0.34   0.735    -.0385631    .0546618
        yr14 |   .0179798   .0237258     0.76   0.449    -.0285219    .0644814
        yr15 |  -.0115345   .0234152    -0.49   0.622    -.0574275    .0343585
        yr16 |  -.0263228   .0233368    -1.13   0.259     -.072062    .0194165
        yr17 |   .0019019    .023264     0.08   0.935    -.0436948    .0474985
        yr18 |  -.0038237   .0231897    -0.16   0.869    -.0492747    .0416273
        yr19 |   .0215469   .0233356     0.92   0.356    -.0241901    .0672838
        yr20 |   .0036934   .0232789     0.16   0.874    -.0419324    .0493193
        yr21 |   .0050649   .0233687     0.22   0.828    -.0407368    .0508667
        yr22 |  -.0160545   .0232246    -0.69   0.489    -.0615739    .0294649
        yr23 |   .0200222   .0231971     0.86   0.388    -.0254433    .0654878
        yr24 |   .0051773   .0232444     0.22   0.824    -.0403809    .0507356
        yr25 |  -.0364671    .023216    -1.57   0.116    -.0819697    .0090355
        yr26 |   .0629364   .0231853     2.71   0.007      .017494    .1083787
        yr27 |   .0028832   .0232247     0.12   0.901    -.0426364    .0484029
        yr28 |   .0017144   .0231843     0.07   0.941     -.043726    .0471548
        yr29 |   .0132832   .0231714     0.57   0.566    -.0321318    .0586983
        yr30 |    .004425   .0232676     0.19   0.849    -.0411787    .0500287
        yr31 |  -.0367104   .0232841    -1.58   0.115    -.0823463    .0089256
        yr32 |   -.011032   .0233507    -0.47   0.637    -.0567986    .0347345
        yr33 |   .0140877   .0230807     0.61   0.542    -.0311496    .0593251
        yr34 |  -.0057824    .023058    -0.25   0.802    -.0509753    .0394105
        yr35 |   .0041397    .023038     0.18   0.857    -.0410139    .0492933
        yr36 |  -.0405128   .0230048    -1.76   0.078    -.0856013    .0045758
        yr37 |  -.0030994   .0230534    -0.13   0.893    -.0482832    .0420844
        yr38 |   .0040511   .0230197     0.18   0.860    -.0410668    .0491689
        yr39 |   .0035858   .0230256     0.16   0.876    -.0415436    .0487152
        yr40 |   .0079728   .0231945     0.34   0.731    -.0374876    .0534333
        yr41 |  -.0181299   .0233019    -0.78   0.437    -.0638007    .0275409
        yr42 |  -.0152946   .0232321    -0.66   0.510    -.0608287    .0302395
        yr43 |   .0048455   .0232524     0.21   0.835    -.0407284    .0504195
        yr44 |   -.025654   .0232216    -1.10   0.269    -.0711674    .0198595
        yr45 |  -.0201522   .0232677    -0.87   0.386    -.0657562    .0254517
        yr46 |   .0215768    .023257     0.93   0.354    -.0240061    .0671597
        yr47 |  -.0027177    .023233    -0.12   0.907    -.0482534    .0428181
        yr48 |  -.0274366   .0232932    -1.18   0.239    -.0730905    .0182172
        yr49 |  -.0159166   .0232996    -0.68   0.495    -.0615831    .0297498
        yr50 |    .012279   .0232845     0.53   0.598    -.0333577    .0579157
------------------------------------------------------------------------------
Instruments for differenced equation
        GMM-type: L(2/.).ln_co2pc_gr
        Standard: D.ln_gdppc_gr D.ei_ch D.res_share_ch D.yr3 D.yr4 D.yr5
                  D.yr6 D.yr7 D.yr8 D.yr9 D.yr10 D.yr11 D.yr12 D.yr13 D.yr14
                  D.yr15 D.yr16 D.yr17 D.yr18 D.yr19 D.yr20 D.yr21 D.yr22
                  D.yr23 D.yr24 D.yr25 D.yr26 D.yr27 D.yr28 D.yr29 D.yr30
                  D.yr31 D.yr32 D.yr33 D.yr34 D.yr35 D.yr36 D.yr37 D.yr38
                  D.yr39 D.yr40 D.yr41 D.yr42 D.yr43 D.yr44 D.yr45 D.yr46
                  D.yr47 D.yr48 D.yr49 D.yr50
Should I change to xtdpdgmm?

Or I should use PVAR o Panel ARDL because is long panel?

Thanks in advance,

Sebastian.