Frequencies for first 10,000 rows of prov1400 variable in pos1991 dataset :

technologis |
        t - |
proficiency |
       exam |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,919       99.19       99.19
          1 |         54        0.54       99.73
          2 |         15        0.15       99.88
          3 |          4        0.04       99.92
          4 |          1        0.01       99.93
          6 |          3        0.03       99.96
          8 |          3        0.03       99.99
          9 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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