Frequencies for first 10,000 rows of prov1320 variable in pos1993 dataset :

 tech super |
 - cytology |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,971       99.71       99.71
          1 |         20        0.20       99.91
          2 |          7        0.07       99.98
          4 |          1        0.01       99.99
        100 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 26 Jan 2016