Hello there,

i have split my sample into two parts and ran a fe regression for both of them.

is it possible to say that one effect ist stroger than the other? can i say that the coefficient of the governance variable in period 2 is stronger than in period 1?

Code:
Linear regression                               Number of obs     =      2,088
                                                F(53, 430)        =          .
                                                Prob > F          =          .
                                                R-squared         =     0.7361
                                                Root MSE          =     .09705

                                         (Std. Err. adjusted for 431 clusters in company_code)
----------------------------------------------------------------------------------------------
                             |               Robust
         return_volatility_w |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-----------------------------+----------------------------------------------------------------
            governance_score |  -.0248947   .0150816    -1.65   0.100    -.0545375    .0047481
              company_size_w |  -.0404233   .0086368    -4.68   0.000    -.0573988   -.0234478
            dividend_ratio_w |  -.8944752    .187322    -4.78   0.000    -1.262656   -.5262946
      earnings_smoothing_2_w |  -.0219127   .0050407    -4.35   0.000    -.0318202   -.0120053
                  leverage_w |   .0228574   .0284547     0.80   0.422    -.0330702    .0787849
research_development_ratio_w |   .0840555    .101191     0.83   0.407    -.1148351    .2829461
              sales_growth_w |  -.0268705   .0161192    -1.67   0.096    -.0585527    .0048118
         tangability_ratio_w |   .0415229   .0149298     2.78   0.006     .0121784    .0708674
             turnover_rate_w |   .0268959   .0016942    15.88   0.000      .023566    .0302258
                 blockholder |   .0008572   .0022735     0.38   0.706    -.0036114    .0053257
        trade_union_coverage |  -.0000485   .0004925    -0.10   0.922    -.0010165    .0009196
                  bank_power |    .387277   .0397159     9.75   0.000     .3092155    .4653385
                             |
                       sic_2 |
                         13  |  -.0304118   .0150801    -2.02   0.044    -.0600516    -.000772
                         20  |  -.1392726   .0161967    -8.60   0.000    -.1711072    -.107438
                         21  |  -.1314665   .0323268    -4.07   0.000    -.1950048   -.0679282
                         22  |  -.1170602   .0116354   -10.06   0.000    -.1399296   -.0941908
                         23  |  -.0864256   .0288507    -3.00   0.003    -.1431315   -.0297196
                         24  |  -.0144642   .0172295    -0.84   0.402    -.0483288    .0194003
                         25  |  -.0491051    .014703    -3.34   0.001    -.0780037   -.0202065
                         26  |  -.0932712   .0265203    -3.52   0.000    -.1453966   -.0411457
                         27  |  -.1102874   .0213453    -5.17   0.000    -.1522415   -.0683332
                         28  |  -.1001355   .0143351    -6.99   0.000    -.1283111     -.07196
                         29  |  -.0705352   .0149799    -4.71   0.000    -.0999782   -.0410922
                         30  |  -.0265549   .0369599    -0.72   0.473    -.0991994    .0460896
                         31  |  -.0848841   .0332142    -2.56   0.011    -.1501664   -.0196017
                         32  |   .0024467   .0159965     0.15   0.879    -.0289944    .0338879
                         33  |   .0167423   .0388873     0.43   0.667    -.0596906    .0931752
                         34  |  -.0953966   .0169065    -5.64   0.000    -.1286262    -.062167
                         35  |  -.0498152   .0162776    -3.06   0.002    -.0818087   -.0178216
                         36  |  -.0549001   .0180429    -3.04   0.002    -.0903634   -.0194368
                         37  |  -.0394992   .0181193    -2.18   0.030    -.0751127   -.0038858
                         38  |  -.1142142   .0159051    -7.18   0.000    -.1454755   -.0829528
                         39  |  -.0832297   .0223976    -3.72   0.000    -.1272521   -.0392072
                         50  |  -.1162061    .024314    -4.78   0.000    -.1639952   -.0684169
                         51  |  -.0762255   .0210122    -3.63   0.000     -.117525   -.0349261
                         52  |   -.090609   .0116039    -7.81   0.000    -.1134164   -.0678016
                         53  |  -.1292317   .0149522    -8.64   0.000    -.1586202   -.0998431
                         54  |  -.1221297   .0142309    -8.58   0.000    -.1501005   -.0941589
                         55  |  -.1201868   .0281467    -4.27   0.000     -.175509   -.0648646
                         56  |  -.0906343   .0237194    -3.82   0.000    -.1372546   -.0440139
                         57  |  -.1217428   .0272069    -4.47   0.000    -.1752178   -.0682678
                         58  |  -.1360863   .0194496    -7.00   0.000    -.1743144   -.0978583
                         59  |  -.0626834   .0200505    -3.13   0.002    -.1020925   -.0232742
                         70  |   .0141774   .0388447     0.36   0.715    -.0621716    .0905265
                         72  |  -.0498467   .0193437    -2.58   0.010    -.0878666   -.0118268
                         73  |  -.0595291   .0167802    -3.55   0.000    -.0925105   -.0265477
                         75  |  -.0240225   .0618428    -0.39   0.698    -.1455743    .0975293
                         78  |  -.0734657   .0236273    -3.11   0.002    -.1199051   -.0270264
                         79  |  -.0495513   .0308397    -1.61   0.109    -.1101666     .011064
                         80  |  -.1468875   .0238443    -6.16   0.000    -.1937534   -.1000217
                         82  |  -.0930031   .0181935    -5.11   0.000    -.1287624   -.0572438
                         87  |  -.0597639   .0310283    -1.93   0.055    -.1207499    .0012221
                             |
                        year |
                       2004  |  -.1906044    .014588   -13.07   0.000     -.219277   -.1619318
                       2005  |   -.490761   .0420629   -11.67   0.000    -.5734355   -.4080864
                       2006  |  -.7040922   .0631446   -11.15   0.000    -.8282028   -.5799817
                       2007  |  -.7784349   .0708597   -10.99   0.000    -.9177093   -.6391604
                       2008  |  -.3461531   .0470228    -7.36   0.000    -.4385762   -.2537299
                       2009  |          0  (omitted)
                             |
                       _cons |   -2.18514   .3043332    -7.18   0.000    -2.783305   -1.586974
----------------------------------------------------------------------------------------------

. 
end of do-file

. do "C:\Users\Paddy\AppData\Local\Temp\STD307c_000000.tmp"

. 
. regress return_volatility_w governance_score company_size_w dividend_ratio_w earnings_smoothing_2_w leverage_w resear
> ch_development_ratio_w sales_growth_w tangability_ratio_w turnover_rate_w blockholder trade_union_coverage bank_power
>  i.sic_2 i.year if year > 2010, vce (cluster company_code)
note: 2019.year omitted because of collinearity

Linear regression                               Number of obs     =      3,134
                                                F(54, 420)        =          .
                                                Prob > F          =          .
                                                R-squared         =     0.6752
                                                Root MSE          =     .06619

                                         (Std. Err. adjusted for 421 clusters in company_code)
----------------------------------------------------------------------------------------------
                             |               Robust
         return_volatility_w |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-----------------------------+----------------------------------------------------------------
            governance_score |  -.0195744   .0086024    -2.28   0.023    -.0364835   -.0026654
              company_size_w |  -.0251767   .0046063    -5.47   0.000    -.0342309   -.0161225
            dividend_ratio_w |  -.6324831   .0940964    -6.72   0.000    -.8174417   -.4475244
      earnings_smoothing_2_w |  -.0057561    .002902    -1.98   0.048    -.0114604   -.0000518
                  leverage_w |   .0344702   .0170789     2.02   0.044     .0008995    .0680409
research_development_ratio_w |   .2468165   .0671307     3.68   0.000     .1148625    .3787705
              sales_growth_w |   .0341093   .0120846     2.82   0.005     .0103555    .0578631
         tangability_ratio_w |   .0181575   .0102887     1.76   0.078    -.0020663    .0383813
             turnover_rate_w |   .0263781   .0017497    15.08   0.000     .0229387    .0298174
                 blockholder |   .0054793   .0015189     3.61   0.000     .0024937    .0084649
        trade_union_coverage |  -.0000215   .0003034    -0.07   0.944    -.0006179    .0005749
                  bank_power |  -.0966771   .0245319    -3.94   0.000    -.1448976   -.0484566
                             |
                       sic_2 |
                         21  |   .0304405   .0172305     1.77   0.078    -.0034283    .0643093
                         22  |  -.0055592   .0282167    -0.20   0.844    -.0610228    .0499044
                         23  |   .0420466   .0417709     1.01   0.315    -.0400596    .1241527
                         24  |   .0224067   .0157591     1.42   0.156    -.0085697    .0533832
                         25  |    .050406   .0108798     4.63   0.000     .0290203    .0717917
                         26  |   -.006852   .0167531    -0.41   0.683    -.0397824    .0260785
                         27  |   .0284892   .0194864     1.46   0.144    -.0098139    .0667923
                         28  |   .0263143   .0120419     2.19   0.029     .0026444    .0499843
                         29  |   .0581011   .0141749     4.10   0.000     .0302385    .0859637
                         30  |   .0381382   .0160436     2.38   0.018     .0066023     .069674
                         31  |   .0727234    .013591     5.35   0.000     .0460085    .0994383
                         32  |   .0307623    .009945     3.09   0.002     .0112141    .0503105
                         33  |   .0098386   .0422816     0.23   0.816    -.0732713    .0929486
                         34  |   .0013414   .0119072     0.11   0.910    -.0220638    .0247465
                         35  |    .038221   .0130557     2.93   0.004     .0125583    .0638836
                         36  |   .0334714    .015186     2.20   0.028     .0036215    .0633213
                         37  |   .0242125   .0139162     1.74   0.083    -.0031415    .0515666
                         38  |  -.0049464   .0118221    -0.42   0.676    -.0281842    .0182913
                         39  |   .0342769   .0152831     2.24   0.025      .004236    .0643178
                         50  |   .0017851   .0166087     0.11   0.914    -.0308614    .0344315
                         51  |   .0551732   .0232763     2.37   0.018     .0094206    .1009257
                         52  |   .0083861   .0131168     0.64   0.523    -.0173966    .0341689
                         53  |  -.0032044    .013684    -0.23   0.815    -.0301021    .0236933
                         54  |   .0099408    .018664     0.53   0.595    -.0267457    .0466273
                         55  |  -.0136201   .0189074    -0.72   0.472     -.050785    .0235449
                         56  |   .0292476   .0178389     1.64   0.102    -.0058171    .0643122
                         57  |   .0104898   .0372296     0.28   0.778    -.0626898    .0836695
                         58  |  -.0067515   .0190734    -0.35   0.724    -.0442427    .0307396
                         59  |   .0356023   .0134419     2.65   0.008     .0091806    .0620239
                         70  |   .0100439   .0273551     0.37   0.714     -.043726    .0638138
                         72  |   .0390487   .0122056     3.20   0.001     .0150571    .0630404
                         73  |   .0164809   .0127765     1.29   0.198    -.0086329    .0415946
                         75  |   .0205875   .0281016     0.73   0.464    -.0346498    .0758248
                         78  |   .0251894   .0122396     2.06   0.040     .0011308    .0492479
                         79  |   .0247439   .0196943     1.26   0.210    -.0139678    .0634556
                         80  |  -.0274531   .0145026    -1.89   0.059    -.0559598    .0010535
                         82  |   .0988074   .0148506     6.65   0.000     .0696166    .1279981
                         87  |   .0399987   .0188036     2.13   0.034     .0030378    .0769596
                             |
                        year |
                       2012  |  -.0734135   .0070246   -10.45   0.000    -.0872213   -.0596057
                       2013  |  -.0924838   .0093868    -9.85   0.000    -.1109348   -.0740328
                       2014  |  -.1007837   .0090648   -11.12   0.000    -.1186018   -.0829656
                       2015  |  -.0743972    .009796    -7.59   0.000    -.0936525   -.0551419
                       2016  |  -.0636849   .0125124    -5.09   0.000    -.0882797   -.0390901
                       2017  |  -.1162378   .0117682    -9.88   0.000    -.1393696    -.093106
                       2018  |  -.0432795   .0077273    -5.60   0.000    -.0584686   -.0280904
                       2019  |          0  (omitted)
                             |
                       _cons |   1.017701   .1710983     5.95   0.000      .681385    1.354016
----------------------------------------------------------------------------------------------