Frequencies for first 10,000 rows of prov1320 variable in pos1995 dataset :

 tech super |
 - cytology |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,974       99.74       99.74
          1 |         19        0.19       99.93
          2 |          6        0.06       99.99
          4 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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