Frequencies for dr_pres variable in vehicle dataset :

     DRIVER |
   PRESENCE |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        569       90.89       90.89
          2 |          1        0.16       91.05
          3 |         56        8.95      100.00
------------+-----------------------------------
      Total |        626      100.00

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