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

   PREVIOUS |
        DWI |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,112       91.12       91.12
          1 |        278        2.78       93.90
          2 |         38        0.38       94.28
          3 |          2        0.02       94.30
          4 |          5        0.05       94.35
         99 |        492        4.92       99.27
          . |         73        0.73      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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