Frequencies for first 10,000 rows of prov1320 variable in pos1991 dataset :

 tech super |
 - cytology |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,971       99.71       99.71
          1 |         21        0.21       99.92
          2 |          7        0.07       99.99
          4 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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