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

   PREVIOUS |
        DWI |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,156       91.56       91.56
          1 |        272        2.72       94.28
          2 |         41        0.41       94.69
          3 |          6        0.06       94.75
          4 |          3        0.03       94.78
         99 |        470        4.70       99.48
          . |         52        0.52      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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