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

   PREVIOUS |
        DWI |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,261       92.61       92.61
          1 |        237        2.37       94.98
          2 |         40        0.40       95.38
          3 |          8        0.08       95.46
          4 |          2        0.02       95.48
         99 |        411        4.11       99.59
          . |         41        0.41      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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