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

   PREVIOUS |
        DWI |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,170       91.70       91.70
          1 |        297        2.97       94.67
          2 |         60        0.60       95.27
          3 |          8        0.08       95.35
          4 |          3        0.03       95.38
          7 |          1        0.01       95.39
         99 |        389        3.89       99.28
          . |         72        0.72      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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