Frequencies for first 10,000 rows of prev_dwi variable in vehicle dataset :

   PREVIOUS |
        DWI |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,126       91.26       91.26
          1 |        316        3.16       94.42
          2 |         72        0.72       95.14
          3 |          4        0.04       95.18
          4 |          2        0.02       95.20
         99 |        417        4.17       99.37
          . |         63        0.63      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 18 Apr 2016