Good afternoon.

The dataset looks like this:

Code:
* Example generated by -dataex-. For more info, type help dataex
clear
input long pais float(year ln_co2pc_gr ln_gdppc_gr co2pc_gr gdppc_gr res_share_ch ei_ch)
1 1970            .           .            .            .          .             .
1 1971    .04318523           .    .04413044            .  -.6838717             .
1 1972  -.003316879           .  -.003311346            .  -.5843963             .
1 1973   .035467148           .   .036103528            . -.19065896             .
1 1974   -.01744461           .  -.017293148            .  1.1816183             .
1 1975   -.04150105           .   -.04065147            . -1.1635613             .
1 1976    .02756405           .   .027947137            .  -.4502255             .
1 1977      .027318           .    .02769508            .   .4519265             .
1 1978   -.01889515           .   -.01871785            .   .7232267             .
1 1979    .03856087           .    .03931371            . -.03159031             .
1 1980  -.033974648           .   -.03340414            .  1.6892276             .
1 1981   -.03340912           .  -.032857135            .   .3562208             .
1 1982  -.029852867           .   -.02941179            .     .22335             .
1 1983   .010718346           .   .010776284            .  .55891395             .
1 1984  -.025982857           .   -.02564822            .   .3025955             .
1 1985   -.09177828           .   -.08769248            .   .2845615             .
1 1986    .06215334           .    .06412572            . -.57471985             .
1 1987   .035816193           .     .0364652            . -.04727695             .
1 1988    .01995754           .   .020158285            . -2.0891473             .
1 1989     -.051548           .   -.05024241            .  -.8556552             .
1 1990   -.08002138           .   -.07690334            .  2.5997005             .
1 1991    .04825544   .07338333    .04943905    .07614343  -.7621235   -.003763424
1 1992   .014944077   .06285858   .015055898   .064876065   .8977495   -.004395153
1 1993   .020612717   .06581497   .020826785    .06802921   .9866562   -.005773365
1 1994    .02478409   .04406929     .0250941    .04505472  .05130513   .0004600968
1 1995  -.012306213  -.04115677  -.012230685   -.04032156   .1040608    .003823304
1 1996    .04091835   .04185772    .04176683    .04274599   -.889446  -.0021086514
1 1997  .0079956055   .06639385   .008027056    .06864754   .5504242  -.0032310374
1 1998   .014033318   .02645588   .014132484    .02680954  .14474016  -.0015993596
1 1999   .029364586  -.04557419    .02980039   -.04455157 -1.4123623    .004682073
1 2000  -.013619423 -.018927574  -.013527458  -.018749123  -.7077209    .006655703
1 2001   -.04242325  -.05601025   -.04153631   -.05447092  1.7975198  -.0001920025
1 2002  -.064777374  -.12618446   -.06272339   -.11854777   .4461319      .0078657
1 2003    .05957603   .07396126     .0613862    .07676546  -.9268353    -.00195185
1 2004    .07559109    .0758953    .07852178    .07884938 -1.3884256  .00006687366
1 2005    .02943516  .074453354   .029872544    .07729475  .53251714   -.005813921
1 2006    .04256248   .06724262    .04348141    .06955548  .10701164  -.0033557636
1 2007    .08056164   .07625961    .08389506    .07924238 -1.0392638  -.0004027938
1 2008    .02333355   .02984524    .02360851    .03029477   .4650531  -.0015919253
1 2009   -.07792091  -.07100487   -.07496273   -.06854227  1.7649453  -.0008191558
1 2010    .07104397    .0862999    .07362857    .09013356   .3953756   -.003054402
1 2011   .036629677   .04797363    .03730834      .049143  .19075124   -.001405331
1 2012   .005539894  -.02078247     .0055553  -.020567933  -.5361876   .0016440516
1 2013   .017653465  .013266563   .017810239    .01335466 .006848871   .0002165544
1 2014   -.02623844 -.035855293  -.025896933  -.035220277   .9186995   .0021337224
1 2015    .01380539  .016727448   .013901046   .016867941 -1.0696038   -.001246282
1 2016  -.014710426 -.031025887  -.014602168   -.03054932   .5231693    .001930914
1 2017  -.024267197   .01653099   -.02397574   .016668873  1.1013072  -.0032586295
1 2018   -.04940796 -.034734726   -.04820735   -.03413885  -.1671047   .0007113228
1 2019   -.03939629 -.031279564      -.03863   -.03079537  -.0826373  .00057273713
1 2020            .           .            .            .          .             .
2 1970            .           .            .            .          .             .
2 1971    .03735685           .    .03806343            .  -3.583941             .
2 1972   .006715775           .   .006738317            .  -3.595976             .
2 1973     .0723815           .    .07506522            .  1.0047908             .
2 1974  -.013946533           .  -.013849764            .  -2.443425             .
2 1975    .06486988           .   .067020305            .  -5.076143             .
2 1976    .06060696           .    .06248108            .   1.480327             .
2 1977    .15053034           .     .1624507            .  -.9558575             .
2 1978    .05724525           .    .05891533            .   -5.38981             .
2 1979     .2042713           .      .226631            .  1.2600955             .
2 1980   .064723015           .   .066863455            .   2.294343             .
2 1981  .0004091263           .  .0004090958            . -4.1512866             .
2 1982  -.010876656           .  -.010817155            .  -1.286386             .
2 1983   -.08180618           .   -.07854988            .  -.2205604             .
2 1984    .02359295           .    .02387344            .  .52316314             .
2 1985   -.05776501           .   -.05612823            .  -.6478212             .
2 1986      .281785           .     .3254935            .  -.4750064             .
2 1987   .062625885           .      .064629            .  -5.436717             .
2 1988   .008115768           .   .008148801            .   .7065676             .
2 1989    .05866051           .    .06041504            . -1.0042635             .
2 1990   -.02052593           .   -.02031715            .   .9601043             .
2 1991 -.0022001266   -.0434866  -.002197118    -.0425546   -.832518     .01618729
2 1992   -.12391949  -.06234837   -.11654889   -.06044444  -1.431724   -.023318866
2 1993  -.013767242 .0041484833   -.01367371  .0041567744  -1.408625   .0024125425
2 1994     .1101904  .016054153      .116491   .016183637   1.988639    .008190635
2 1995   .034041405  .015937805    .03462734     .0160664 -1.8642867    .006239843
2 1996     .0448246  .034890175    .04584408   .035505243   .2397784   .0004650287
2 1997    .12469387   .04205894     .1328022    .04295658  -.6353271      .0079945
2 1998   -.02123642  .032331467  -.021012744   .032859545  .59386986    -.00912828
2 1999    .05735397 -.000790596    .05903048 -.0007899858   -2.49613    .004564094
2 2000    .04701233   .03958511    .04813543    .04037887   2.706013    .004879483
2 2001   -.04536247 -.027560234   -.04434931   -.02718382 -1.0512298    -.00504469
2 2002  -.015072823 .0044546127  -.014959444   .004464366  .05328191   -.002887168
2 2003  .0005598068  .018220901 .00055978925   .018387806 -.10914221   -.002539354
2 2004   .012296677  .010541916   .012372726   .010597872  -.2341628 -.00010549345
2 2005   .017718315  .035025597   .017876115   .035645753   .7751106   -.003184567
2 2006   .008773804    .0531826   .008812081    .05462261 -1.2377497    -.00716155
2 2007   .010412216   .01738453   .010466738   .017535998   .3962357  -.0003483627
2 2008    .15820885  .002524376     .1714113   .002528249   -.927561     .01863219
2 2009  -.035902023  -.05624008   -.03526547   -.05468835   .4229553    .003304608
2 2010   -.07738018  -.02677727   -.07446237   -.02642146  -.8142483    -.00818127
2 2011     .0507679 -.009784698    .05207909    -.0097374  -.3567042    .007837007
2 2012   -.06547451 -.007086754   -.06337695   -.00706133 -.08397305  -.0083234655
2 2013   .010436058 -.016260147   .010490787  -.016129091  -1.083137   .0025542805
2 2014   -.09462738 -.003108978   -.09028804  -.003103939  .20679207    -.01407241
2 2015  -.010979652  .022444725  -.010919874   .022698896 -1.1899234   -.004809058
2 2016   -.06432438  .022831917   -.06229942   .023094524   .5234437   -.009212221
2 2017   .026329994   .00321579   .026679393    .00322063   .5948993    .004054799
2 2018    .01234913 -.007247925   .012426493  -.007221923   .7516962    .000632762
end
label values pais pais
label def pais 1 "Argentina", modify
label def pais 2 "Barbados", modify
In the example appear two country, but I have many more, 25.

My problem is the following.

When I execute:

Code:
xtunitroot ips ln_co2pc_gr ln_gdppc_gr if year > 1990 & year <2020
I receive a message:

too many variables specified
r(103);

It only works if I use one variable:

Code:
xtunitroot ips ln_co2pc_gr if year > 1990 & year <2020
Is It equivalent if I do one test by variable to do one test with all variables?

What's the problem?

Thank you for any answers and help!