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  • Problem with prob>F and vce(robust)

    Hello,

    I'm posting this message because I have some questions about my data.
    I have about 3,200 data spread over 29 different countries. I want to show the impact of culture on my dependent variable (I also integrate interactions).
    I use the vce(robust) option to have standard errors.
    When I run my regressions for the full sample, everything looks good (low VIF, prob>F = 0.0000, non-significant omitted variables test, etc.). The problem is that my data linked to the USA represents 40% of the sample, so for robustness analysis, I remove this data and run my regressions again.
    This time I no longer have the prob>F (I have "."). The same applies if I remove the data for Canada (which only represents 8% of the database).

    Here is the command :
    Code:
    regress car55_w DGEN centPERF c.centPERF#i.DGEN c.QUOTA#i.DGEN c.centSIZE#i.DGEN i.DGEN#c.centBWOMEN AGE  centSIZE INDEP centBWOMEN DUALITY DEBTRATIO MARKETCAP_w BM_w ROA_w LNCommonSharesOutstanding_w UNEMPL POPGROWTH CORRUP INTEGRATION GDP LEGAL QUOTAS PHD CA MBA MA LAW EXP BUSY ln_AGEXE i.Year  i.FESIZE2, vce(robust)
    As you can see, I include indicator variables for the year and the company's size. Are my results compromised because of this? Knowing that if I remove the vce(robust) option I see my prob>F statistic (which has gone from 0.0000 in the full sample to 0.0600 in the reduced sample).

    I appreciate any help you can provide.

    ps: I'll show you the two regression results with the full sample and the reduced sample

    Full sample:

    Code:
    Linear regression                               Number of obs     =      3,196
                                                    F(55, 3140)       =      95.08
                                                    Prob > F          =     0.0000
                                                    R-squared         =     0.0295
                                                    Root MSE          =     .06839
    
    ---------------------------------------------------------------------------------------------
                                |               Robust
                        car55_w | Coefficient  std. err.      t    P>|t|     [95% conf. interval]
    ----------------------------+----------------------------------------------------------------
                           DGEN |  -.0007034   .0029022    -0.24   0.809    -.0063939    .0049871
                      centFUTUR |  -.0007972   .0071607    -0.11   0.911    -.0148373     .013243
                                |
               DGEN#c.centFUTUR |
                             1  |   .0448187   .0154657     2.90   0.004     .0144948    .0751427
                                |
                  DGEN#c.QUOTAS |
                             1  |   .0288507   .0111366     2.59   0.010      .007015    .0506863
                                |
                DGEN#c.centSIZE |
                             1  |  -.0019211   .0009756    -1.97   0.049    -.0038341   -8.17e-06
                                |
              DGEN#c.centBWOMEN |
                             1  |   .0454247   .0290884     1.56   0.118    -.0116096     .102459
                                |
                            AGE |  -.0013216   .0013604    -0.97   0.331    -.0039891    .0013458
                       centSIZE |  -.0003165   .0005469    -0.58   0.563    -.0013889     .000756
                          INDEP |  -.0057062   .0075767    -0.75   0.451     -.020562    .0091495
                     centBWOMEN |  -.0137267   .0150495    -0.91   0.362    -.0432346    .0157812
                        DUALITY |   .0039083   .0027764     1.41   0.159    -.0015354    .0093521
                      DEBTRATIO |   .0044042     .00883     0.50   0.618    -.0129089    .0217173
                    MARKETCAP_w |  -.0012352   .0015185    -0.81   0.416    -.0042125    .0017422
                           BM_w |   -.002517   .0028371    -0.89   0.375    -.0080797    .0030458
                          ROA_w |  -.0345445   .0175011    -1.97   0.048    -.0688593   -.0002297
    LNCommonSharesOutstanding_w |   .0009978   .0013187     0.76   0.449    -.0015877    .0035834
                         UNEMPL |   .0003852   .0003876     0.99   0.320    -.0003746    .0011451
                      POPGROWTH |   .0055129   .0037465     1.47   0.141    -.0018329    .0128587
                         CORRUP |   .0034896   .0028474     1.23   0.220    -.0020933    .0090725
                    INTEGRATION |   .0047318   .0029201     1.62   0.105    -.0009937    .0104573
                            GDP |   .0030491   .0016574     1.84   0.066    -.0002005    .0062987
                          LEGAL |  -.0038553   .0053843    -0.72   0.474    -.0144124    .0067017
                         QUOTAS |   .0004738   .0063233     0.07   0.940    -.0119244    .0128719
                            PHD |   .0013761   .0040603     0.34   0.735     -.006585    .0093372
                             CA |  -.0194509   .0130981    -1.49   0.138    -.0451327    .0062309
                            MBA |  -.0008793   .0029929    -0.29   0.769    -.0067476     .004989
                             MA |   -.002767   .0036924    -0.75   0.454    -.0100067    .0044728
                            LAW |  -.0046762    .005536    -0.84   0.398    -.0155307    .0061784
                            EXP |  -.0072091   .0033822    -2.13   0.033    -.0138405   -.0005776
                           BUSY |   .0034211   .0033058     1.03   0.301    -.0030606    .0099028
                       ln_AGEXE |   .0131108   .0092635     1.42   0.157    -.0050524     .031274
                                |
                           Year |
                          2003  |   .0159833   .0194859     0.82   0.412     -.022223    .0541897
                          2004  |  -.0161759    .015624    -1.04   0.301    -.0468103    .0144585
                          2005  |  -.0009112   .0162589    -0.06   0.955    -.0327903     .030968
                          2006  |  -.0013393   .0141565    -0.09   0.925    -.0290963    .0264177
                          2007  |  -.0026169    .014224    -0.18   0.854    -.0305062    .0252723
                          2008  |   .0010135   .0149915     0.07   0.946    -.0283807    .0304078
                          2009  |  -.0028215   .0144292    -0.20   0.845    -.0311131    .0254702
                          2010  |  -.0093062   .0131572    -0.71   0.479    -.0351038    .0164913
                          2011  |  -.0169854   .0133098    -1.28   0.202    -.0430821    .0091114
                          2012  |  -.0148416   .0134009    -1.11   0.268    -.0411169    .0114338
                          2013  |  -.0110633   .0128892    -0.86   0.391    -.0363354    .0142088
                          2014  |  -.0096998   .0130592    -0.74   0.458    -.0353051    .0159056
                          2015  |  -.0053336   .0127978    -0.42   0.677    -.0304265    .0197592
                          2016  |  -.0089414   .0127195    -0.70   0.482    -.0338807     .015998
                          2017  |  -.0074988   .0127983    -0.59   0.558    -.0325926     .017595
                          2018  |  -.0194639   .0130291    -1.49   0.135    -.0450104    .0060826
                          2019  |  -.0054806   .0133076    -0.41   0.680    -.0315729    .0206118
                                |
                        FESIZE2 |
                             2  |   .2563835   .0225849    11.35   0.000     .2121009     .300666
                             3  |   .2348571   .0101594    23.12   0.000     .2149374    .2547767
                             4  |   .2337393   .0106437    21.96   0.000     .2128699    .2546086
                             5  |   .2408719   .0118452    20.33   0.000     .2176468    .2640971
                             6  |   .2411293   .0137035    17.60   0.000     .2142606    .2679979
                             7  |   .2416817   .0169828    14.23   0.000     .2083832    .2749801
                             8  |   .2505442    .020197    12.41   0.000     .2109435     .290145
                                |
                          _cons |  -.3608112   .0730594    -4.94   0.000    -.5040603   -.2175622

    Reduced sample:

    Code:
    Linear regression                               Number of obs     =      1,593
                                                    F(53, 1537)       =          .
                                                    Prob > F          =          .
                                                    R-squared         =     0.0443
                                                    Root MSE          =     .07167
    
    ---------------------------------------------------------------------------------------------
                                |               Robust
                        car55_w | Coefficient  std. err.      t    P>|t|     [95% conf. interval]
    ----------------------------+----------------------------------------------------------------
                           DGEN |   .0067783    .005162     1.31   0.189     -.003347    .0169035
                      centFUTUR |   .0000168   .0072818     0.00   0.998    -.0142664    .0143001
                                |
               DGEN#c.centFUTUR |
                             1  |   .0340473   .0167192     2.04   0.042     .0012524    .0668423
                                |
                  DGEN#c.QUOTAS |
                             1  |   .0226001    .012364     1.83   0.068    -.0016519    .0468522
                                |
                DGEN#c.centSIZE |
                             1  |  -.0016121   .0012494    -1.29   0.197    -.0040627    .0008386
                                |
              DGEN#c.centBWOMEN |
                             1  |   .0314506   .0435058     0.72   0.470    -.0538865    .1167876
                                |
                            AGE |  -.0040321   .0019804    -2.04   0.042    -.0079167   -.0001475
                       centSIZE |  -.0005461    .000653    -0.84   0.403    -.0018269    .0007347
                          INDEP |  -.0074823   .0095797    -0.78   0.435    -.0262729    .0113084
                     centBWOMEN |  -.0040372   .0201498    -0.20   0.841    -.0435611    .0354868
                        DUALITY |   .0043646   .0044447     0.98   0.326    -.0043537     .013083
                      DEBTRATIO |   .0109233   .0132116     0.83   0.408    -.0149913    .0368379
                    MARKETCAP_w |  -.0027462   .0020072    -1.37   0.171    -.0066832    .0011909
                           BM_w |  -.0017192   .0033959    -0.51   0.613    -.0083803    .0049419
                          ROA_w |   .0027042   .0275708     0.10   0.922    -.0513762    .0567845
    LNCommonSharesOutstanding_w |  -.0006544   .0016692    -0.39   0.695    -.0039285    .0026197
                         UNEMPL |   .0003371   .0004319     0.78   0.435    -.0005101    .0011842
                      POPGROWTH |   .0042424   .0039422     1.08   0.282    -.0034904    .0119751
                         CORRUP |   .0021214   .0033061     0.64   0.521    -.0043636    .0086065
                    INTEGRATION |   .0039104   .0032206     1.21   0.225    -.0024068    .0102276
                            GDP |   .0028411   .0027489     1.03   0.302     -.002551    .0082332
                          LEGAL |  -.0011298   .0054773    -0.21   0.837    -.0118735    .0096138
                         QUOTAS |   .0001542   .0070254     0.02   0.982    -.0136263    .0139347
                            PHD |   .0058123   .0058507     0.99   0.321     -.005664    .0172885
                             CA |  -.0191117    .013741    -1.39   0.164    -.0460648    .0078414
                            MBA |    .001409   .0046287     0.30   0.761    -.0076701    .0104881
                             MA |  -.0005586   .0050308    -0.11   0.912    -.0104265    .0093093
                            LAW |  -.0122426   .0097059    -1.26   0.207    -.0312809    .0067957
                            EXP |  -.0126975   .0050337    -2.52   0.012     -.022571   -.0028239
                           BUSY |   .0022522   .0049623     0.45   0.650    -.0074813    .0119857
                       ln_AGEXE |   .0211569   .0138933     1.52   0.128    -.0060949    .0484087
                                |
                           Year |
                          2003  |  -.0145246   .0292096    -0.50   0.619    -.0718194    .0427702
                          2004  |  -.0338672     .01575    -2.15   0.032    -.0647608   -.0029735
                          2005  |  -.0452805    .013995    -3.24   0.001    -.0727319   -.0178291
                          2006  |  -.0304899   .0143438    -2.13   0.034    -.0586253   -.0023545
                          2007  |  -.0346337   .0174599    -1.98   0.047    -.0688814    -.000386
                          2008  |  -.0234888   .0170425    -1.38   0.168    -.0569179    .0099403
                          2009  |   -.023938   .0155296    -1.54   0.123    -.0543994    .0065235
                          2010  |  -.0324411   .0136871    -2.37   0.018    -.0592884   -.0055938
                          2011  |   -.052807   .0138124    -3.82   0.000    -.0799002   -.0257139
                          2012  |  -.0457398   .0141955    -3.22   0.001    -.0735844   -.0178953
                          2013  |  -.0391303   .0124888    -3.13   0.002    -.0636271   -.0146335
                          2014  |  -.0369942   .0129445    -2.86   0.004     -.062385   -.0116034
                          2015  |  -.0387998   .0126482    -3.07   0.002    -.0636095   -.0139902
                          2016  |  -.0357512   .0131008    -2.73   0.006    -.0614484   -.0100539
                          2017  |  -.0369101   .0123544    -2.99   0.003    -.0611434   -.0126769
                          2018  |  -.0532437   .0130374    -4.08   0.000    -.0788167   -.0276708
                          2019  |   -.029239    .013521    -2.16   0.031    -.0557605   -.0027175
                                |
                        FESIZE2 |
                             2  |   .2359234   .0778803     3.03   0.002     .0831606    .3886863
                             3  |    .242945   .0160831    15.11   0.000     .2113978    .2744921
                             4  |   .2434875   .0153902    15.82   0.000     .2132996    .2736754
                             5  |   .2552508   .0169289    15.08   0.000     .2220447    .2884569
                             6  |   .2562097    .019285    13.29   0.000      .218382    .2940374
                             7  |   .2652543   .0216385    12.26   0.000     .2228102    .3076983
                             8  |   .2817825   .0260609    10.81   0.000     .2306638    .3329012
                                |
                          _cons |  -.2921799    .110172    -2.65   0.008    -.5082832   -.0760767

  • #2
    missing F often occurs when you have singletons.

    Comment


    • #3
      Thank you very much for your time,

      Indeed, when we remove the singletons, I find the prob>F.

      I have one last question:
      By removing the observations linked to Canada for a robustness analysis (about 10% of the database), my model is no longer significant (prob>F > 0.10). When I look at the coefficients of the FESIZE2 indicator variables, my coefficients are no longer significant (unlike the full model).

      Do you have any advice on how to solve this problem?

      Thank you in advance for your help.

      Here is the result of the regression on the reduced sample:

      Code:
      Linear regression                               Number of obs     =      2,936
                                                      F(54, 2881)       =       1.14
                                                      Prob > F          =     0.2234
                                                      R-squared         =     0.0202
                                                      Root MSE          =      .0661
      
      ---------------------------------------------------------------------------------------------
                                  |               Robust
                          car55_w | Coefficient  std. err.      t    P>|t|     [95% conf. interval]
      ----------------------------+----------------------------------------------------------------
                             DGEN |  -.0033336    .002965    -1.12   0.261    -.0091473    .0024801
                        centFUTUR |   .0004357   .0069871     0.06   0.950    -.0132644    .0141358
                                  |
                 DGEN#c.centFUTUR |
                               1  |   .0310375   .0168362     1.84   0.065    -.0019746    .0640496
                                  |
                    DGEN#c.QUOTAS |
                               1  |   .0276952   .0113379     2.44   0.015      .005464    .0499264
                                  |
                  DGEN#c.centSIZE |
                               1  |  -.0019991   .0010402    -1.92   0.055    -.0040386    .0000405
                                  |
                DGEN#c.centBWOMEN |
                               1  |   .0538094   .0293964     1.83   0.067    -.0038307    .1114494
                                  |
                              AGE |  -.0010139   .0013671    -0.74   0.458    -.0036945    .0016667
                         centSIZE |  -.0003245    .000554    -0.59   0.558    -.0014107    .0007618
                            INDEP |  -.0093762   .0076051    -1.23   0.218    -.0242882    .0055357
                       centBWOMEN |  -.0170519   .0150913    -1.13   0.259    -.0466427    .0125389
                          DUALITY |    .003354   .0027852     1.20   0.229    -.0021072    .0088151
                        DEBTRATIO |   .0007347   .0090768     0.08   0.935     -.017063    .0185324
                      MARKETCAP_w |  -.0015306   .0015484    -0.99   0.323    -.0045668    .0015055
                             BM_w |  -.0045428   .0029934    -1.52   0.129    -.0104122    .0013266
                            ROA_w |  -.0296593   .0176017    -1.69   0.092    -.0641725    .0048538
      LNCommonSharesOutstanding_w |   .0009692    .001354     0.72   0.474    -.0016857     .003624
                           UNEMPL |   .0004618   .0003882     1.19   0.234    -.0002993     .001223
                        POPGROWTH |   .0059228   .0036586     1.62   0.106     -.001251    .0130966
                           CORRUP |   .0033642   .0029438     1.14   0.253     -.002408    .0091364
                      INTEGRATION |    .004927    .002988     1.65   0.099    -.0009319    .0107859
                              GDP |   .0033964   .0017212     1.97   0.049     .0000215    .0067712
                            LEGAL |  -.0041198    .005497    -0.75   0.454    -.0148983    .0066587
                           QUOTAS |    .000224   .0063101     0.04   0.972    -.0121488    .0125969
                              PHD |   .0012947   .0040747     0.32   0.751    -.0066948    .0092842
                               CA |  -.0084361   .0126694    -0.67   0.506    -.0332781    .0164059
                              MBA |  -.0007969   .0030446    -0.26   0.794    -.0067668    .0051729
                               MA |  -.0014945   .0037534    -0.40   0.691    -.0088541    .0058651
                              LAW |  -.0001483   .0060685    -0.02   0.981    -.0120473    .0117506
                              EXP |  -.0051336   .0033663    -1.52   0.127    -.0117342     .001467
                             BUSY |    .002782   .0032644     0.85   0.394    -.0036189    .0091829
                         ln_AGEXE |   .0115216   .0094327     1.22   0.222     -.006974    .0300171
                                  |
                             Year |
                            2003  |   .0333775   .0209448     1.59   0.111    -.0076908    .0744457
                            2004  |   .0002716   .0155504     0.02   0.986    -.0302194    .0307627
                            2005  |   .0140449   .0163166     0.86   0.389    -.0179485    .0460383
                            2006  |   .0085303   .0140128     0.61   0.543    -.0189457    .0360064
                            2007  |   .0102236   .0135451     0.75   0.450    -.0163355    .0367826
                            2008  |   .0118477   .0148852     0.80   0.426    -.0173391    .0410344
                            2009  |   .0072613   .0135758     0.53   0.593    -.0193581    .0338806
                            2010  |   .0012092   .0124994     0.10   0.923    -.0232994    .0257178
                            2011  |  -.0016117   .0126339    -0.13   0.898    -.0263842    .0231607
                            2012  |  -.0001005   .0128706    -0.01   0.994     -.025337    .0251359
                            2013  |   .0012699   .0121913     0.10   0.917    -.0226347    .0251744
                            2014  |   .0036623   .0124063     0.30   0.768    -.0206637    .0279884
                            2015  |   .0068628   .0120407     0.57   0.569    -.0167464     .030472
                            2016  |   .0038543   .0119535     0.32   0.747     -.019584    .0272926
                            2017  |    .003989    .012083     0.33   0.741    -.0197032    .0276811
                            2018  |  -.0041905   .0123407    -0.34   0.734     -.028388     .020007
                            2019  |   .0069226   .0127163     0.54   0.586    -.0180114    .0318565
                                  |
                          FESIZE2 |
                               3  |  -.0118369   .0220945    -0.54   0.592    -.0551595    .0314857
                               4  |  -.0129536   .0222511    -0.58   0.561    -.0565833    .0306761
                               5  |  -.0064982   .0228135    -0.28   0.776    -.0512307    .0382343
                               6  |  -.0048252   .0239851    -0.20   0.841     -.051855    .0422046
                               7  |  -.0039719   .0263068    -0.15   0.880     -.055554    .0476101
                               8  |   .0042566   .0286992     0.15   0.882    -.0520163    .0605296
                                  |
                            _cons |   -.120905   .0806921    -1.50   0.134    -.2791251    .0373151
      ---------------------------------------------------------------------------------------------

      Comment


      • #4

        Wow. Either Canada is driving the whole thing, or you may have data problems. Why don't you have a country fixed effect? You might try areg or regdhfe and absorb(COUNTRY YEAR FESIZE2) if you're not interested in those coefficients. Doing so will give you a few more degrees of freedom, but not solve this swing, especially given the large sample size. Also cluster on COUNTRY; with 29 you should be good. Check for low observation counts in countries. You've got a rich model and that could be a problem.

        Your F-stat appears to be driven by year/fesize.
        Last edited by George Ford; 20 May 2024, 15:42.

        Comment


        • #5
          Thank you very much for your reply,

          I don't use a country fixed effect, because my variables of interest are the culture of the countries (score per country constant over the years) and so I avoid multicollinearity.

          I've tried your methods, but I can't find the prob>F statistic with the vce(cluster country). This is not linked to singletons.

          Thank you all the same for your time,

          Comment


          • #6
            I see.

            If you don't have a country FE, then I'd worry the culture variable (fixed over time in a country) is representing far more than just culture.

            Look into Mundlak regression. You can get a coefficient on culture even accounting for country.

            Code:
            ssc install mundlak

            Comment

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