Frequencies for first 10,000 rows of prov1340 variable in pos1991 dataset :

 tech super |
          - |
immunohemat |
      ology |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,789       97.89       97.89
          1 |        169        1.69       99.58
          2 |         34        0.34       99.92
          3 |          2        0.02       99.94
          4 |          6        0.06      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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