Frequencies for first 10,000 rows of prov1350 variable in pos1991 dataset :

 tech super |
          - |
microbiolog |
          y |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,720       97.20       97.20
          1 |        226        2.26       99.46
          2 |         48        0.48       99.94
          3 |          1        0.01       99.95
          4 |          3        0.03       99.98
          5 |          2        0.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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