st: svy, subpop ( ) with version 10

["Leda Inga" <ledainga@gmail.com>]

Hi,

I'm running a logit using svy and found a difference in the
coefficients and pvalues reported by version 9 and 10 of Stata. I
thought that it could be because of the observations that each one
takes into account. As you can see below the version 10 considers 4178
observations but  there are actually 8471 and the results are the same
as using the "if" after svy. Can anybody explain this?

The command I used for both versions was:

svy, subpop(urbano): logit PS n_hijos educ seguro V157 NSE rural
_ISREGION_3 _ISREGION_5 CPci CPci2 labor_prol

VERSION 10:

Survey: Logistic regression

Number of strata   =        24                  Number of obs      =      4178
Number of PSUs   =       451                 Population size    = 2920.9792

                            Subpop. no. of obs =      4178
                                                          Subpop. size
      = 2920.9792
                                                          Design df
      =       427
                                                          F(  10,
418)    =     30.43
                                                          Prob > F
      =    0.0000

------------------------------------------------------------------------------
             |             Linearized
          PS |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
     n_hijos |  -.0627022   .0233953    -2.68   0.008    -.1086865   -.0167179
        educ |   .0995025   .0176722     5.63   0.000     .0647671    .1342379
      seguro |   .2691795   .1430446     1.88   0.061    -.0119797    .5503387
        V157 |   .2184025   .0961237     2.27   0.024     .0294679    .4073371
         NSE |   .5893834   .0859681     6.86   0.000     .4204101    .7583568
_ISREGION_3 |  -.8503491   .2073588    -4.10   0.000     -1.25792   -.4427781
_ISREGION_5 |  -.7629466   .2529318    -3.02   0.003    -1.260093   -.2658003
        CPci |    .298412   .0547975     5.45   0.000     .1907057    .4061184
       CPci2 |  -.0109094   .0043379    -2.51   0.012    -.0194356   -.0023832
  labor_prol |    .415821   .1035528     4.02   0.000     .2122843    .6193578
       _cons |  -2.961981   .3026012    -9.79   0.000    -3.556754   -2.367207
------------------------------------------------------------------------------
Note: 25 strata omitted because they contain no subpopulation members.


VERSION 9:

Survey: Logistic regression

Number of strata   =        49                  Number of obs      =      8471
Number of PSUs   =      1118                 Population size    =  6948.092
                                                          Subpop. no.
of obs =      4212
                                                          Subpop. size
      = 2945.3116
                                                          Design df
      =      1069
                                                          F(  10,
1060)    =     31.19
                                                          Prob > F
      =    0.0000

------------------------------------------------------------------------------
             |             Linearized
          PS |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
     n_hijos |  -.0624413    .023198    -2.69   0.007      -.10796   -.0169225
        educ |    .100353   .0178213     5.63   0.000     .0653842    .1353218
      seguro |   .2789113   .1415214     1.97   0.049     .0012202    .5566025
        V157 |   .2192173   .0962575     2.28   0.023     .0303421    .4080924
         NSE |   .5896208   .0851999     6.92   0.000     .4224427    .7567989
_ISREGION_3 |  -.8230625   .2058183    -4.00   0.000    -1.226916   -.4192088
_ISREGION_5 |  -.7412179   .2491071    -2.98   0.003    -1.230012   -.2524236
        CPci |   .2921813     .04976     5.87   0.000      .194543    .3898195
       CPci2 |  -.0103967   .0037064    -2.81   0.005    -.0176694    -.003124
  labor_prol |   .4267068   .1025795     4.16   0.000     .2254268    .6279867
       _cons |   -2.97932    .293572   -10.15   0.000    -3.555362   -2.403277
------------------------------------------------------------------------------


Thanks.
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