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

   PREVIOUS |
        DWI |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,161       91.61       91.61
          1 |        258        2.58       94.19
          2 |         29        0.29       94.48
          3 |          2        0.02       94.50
          4 |          1        0.01       94.51
         99 |        468        4.68       99.19
          . |         81        0.81      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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