Frequencies for first 10,000 rows of prov2420 variable in pos1999 dataset :

       srv: |
psychologic |
         al |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,932       99.32       99.32
          0 |         23        0.23       99.55
          1 |         12        0.12       99.67
          2 |         16        0.16       99.83
          3 |         17        0.17      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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