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       log:  d:\bill\fall2008\econ30331\kentucky.log
  log type:  text
 opened on:   8 Nov 2008, 15:09:18

. 
. 
. * generate log duration
. gen ldurat=ln(durat)

. 
. * sort the data by highearn and afchnge
. sort highearn afchnge

. 
. * gets means of ldurat for
. * 2x2 table
. by highearn afchnge: sum ldurat

-------------------------------------------------------------------------------
-> highearn = 0, afchnge = 0

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
      ldurat |      1652    1.123241    1.227601  -1.386294   5.204007

-------------------------------------------------------------------------------
-> highearn = 0, afchnge = 1

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
      ldurat |      1464    1.137382    1.273859  -1.386294   5.204007

-------------------------------------------------------------------------------
-> highearn = 1, afchnge = 0

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
      ldurat |      1128     1.35583    1.254325  -1.386294   5.204007

-------------------------------------------------------------------------------
-> highearn = 1, afchnge = 1

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
      ldurat |      1103    1.599077    1.302141  -1.386294   5.204007


. 
. 
. * get the treatment effect
. gen treat=highearn*afchnge

. 
. * run difference in difference regression
. reg ldurat highearn afchnge treat

      Source |       SS       df       MS              Number of obs =    5347
-------------+------------------------------           F(  3,  5343) =   39.58
       Model |  188.983823     3  62.9946077           Prob > F      =  0.0000
    Residual |  8503.76169  5343   1.5915706           R-squared     =  0.0217
-------------+------------------------------           Adj R-squared =  0.0212
       Total |  8692.74552  5346  1.62602797           Root MSE      =  1.2616

------------------------------------------------------------------------------
      ldurat |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
    highearn |   .2325891   .0487277     4.77   0.000     .1370629    .3281152
     afchnge |   .0141418   .0452831     0.31   0.755    -.0746316    .1029151
       treat |   .2291051   .0700319     3.27   0.001      .091814    .3663963
       _cons |   1.123241    .031039    36.19   0.000     1.062391     1.18409
------------------------------------------------------------------------------

. 
. 
. * get other covariate
. gen lage=ln(age)

. gen lprewage=ln(prewage)

. gen high_x_lpre=highearn*lprewage

. 
. xi i.industry i.injury
i.industry        _Iindustry_1-3      (naturally coded; _Iindustry_1 omitted)
i.injury          _Iinjury_1-8        (naturally coded; _Iinjury_1 omitted)

. 
. * this next regression replicates the results in 
. * column (i) of table 6, page 336
. 
. reg ldurat highearn afchnge treat male married lage lprewage high_x_lpre _I*

      Source |       SS       df       MS              Number of obs =    5347
-------------+------------------------------           F( 17,  5329) =   16.09
       Model |  424.366738    17  24.9627493           Prob > F      =  0.0000
    Residual |  8268.37878  5329  1.55158168           R-squared     =  0.0488
-------------+------------------------------           Adj R-squared =  0.0458
       Total |  8692.74552  5346  1.62602797           Root MSE      =  1.2456

------------------------------------------------------------------------------
      ldurat |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
    highearn |  -1.522196   1.099035    -1.39   0.166    -3.676755    .6323633
     afchnge |   .0155081   .0447622     0.35   0.729     -.072244    .1032603
       treat |   .2146878   .0693106     3.10   0.002     .0788106     .350565
        male |  -.0722981    .046195    -1.57   0.118    -.1628593    .0182631
     married |   .0509362   .0409132     1.24   0.213    -.0292704    .1311427
        lage |   .2522586   .0522575     4.83   0.000     .1498124    .3547047
    lprewage |   .2582666   .1038422     2.49   0.013     .0546934    .4618397
 high_x_lpre |   .2318765    .187021     1.24   0.215    -.1347612    .5985142
_Iindustry_2 |   .2488065   .0593033     4.20   0.000     .1325477    .3650652
_Iindustry_3 |   .1725146   .0416086     4.15   0.000     .0909448    .2540844
  _Iinjury_2 |    .780188    .155637     5.01   0.000     .4750758      1.0853
  _Iinjury_3 |   .3478323   .0920231     3.78   0.000     .1674295    .5282352
  _Iinjury_4 |   .6341329   .1005691     6.31   0.000     .4369763    .8312895
  _Iinjury_5 |   .5009463   .0924541     5.42   0.000     .3196985    .6821942
  _Iinjury_6 |   .3952596   .0932006     4.24   0.000     .2125482    .5779711
  _Iinjury_7 |   .7892506   .2065032     3.82   0.000     .3844198    1.194081
  _Iinjury_8 |   .5108587   .1288234     3.97   0.000     .2583122    .7634052
       _cons |  -1.605611   .5647855    -2.84   0.004    -2.712822   -.4984007
------------------------------------------------------------------------------

. 
. 
. 
end of do-file

. log close
       log:  d:\bill\fall2008\econ30331\kentucky.log
  log type:  text
 closed on:   8 Nov 2008, 15:09:53
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