Frequencies for first 10,000 rows of spec variable in namcs1994 dataset :

  physician |
  specialty |      Freq.     Percent        Cum.
------------+-----------------------------------
        ADL |         31        0.31        0.31
         CD |         15        0.15        0.46
          D |         55        0.55        1.01
         EM |         19        0.19        1.20
        END |         39        0.39        1.59
         FP |      2,450       24.50       26.09
         GE |         19        0.19       26.28
         GP |      2,496       24.96       51.24
        GPM |         35        0.35       51.59
         GS |        104        1.04       52.63
         IM |      3,031       30.31       82.94
          N |         80        0.80       83.74
        NEP |         12        0.12       83.86
        NPM |         24        0.24       84.10
        OBG |        128        1.28       85.38
         OM |         10        0.10       85.48
        OPH |        113        1.13       86.61
        ORS |        104        1.04       87.65
         OS |         20        0.20       87.85
          P |        126        1.26       89.11
         PD |        759        7.59       96.70
        PDA |         62        0.62       97.32
        PDC |         15        0.15       97.47
        PDE |         10        0.10       97.57
         PM |        126        1.26       98.83
         PS |         24        0.24       99.07
        PUD |         59        0.59       99.66
          U |         34        0.34      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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