Frequencies for first 10,000 rows of spec variable in namcs1993 dataset :

  physician |
  specialty |      Freq.     Percent        Cum.
------------+-----------------------------------
        ADL |         48        0.48        0.48
         AI |         23        0.23        0.71
         CD |         23        0.23        0.94
        CRS |         13        0.13        1.07
          D |         96        0.96        2.03
         EM |         38        0.38        2.41
         FP |      1,601       16.01       18.42
         GE |         52        0.52       18.94
         GP |      2,738       27.38       46.32
         GS |      1,166       11.66       57.98
        HEM |         37        0.37       58.35
         ID |         11        0.11       58.46
         IM |      2,003       20.03       78.49
        OBG |         34        0.34       78.83
        OPH |         53        0.53       79.36
        ORS |         78        0.78       80.14
          P |         56        0.56       80.70
         PD |      1,717       17.17       97.87
        PDA |         55        0.55       98.42
        PDC |         16        0.16       98.58
         PM |         23        0.23       98.81
         PS |         54        0.54       99.35
          U |         23        0.23       99.58
         VS |         42        0.42      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016