Frequencies for dr_pres variable in vehicle dataset :

     DRIVER |
   PRESENCE |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        714       93.46       93.46
          2 |          2        0.26       93.72
          3 |         48        6.28      100.00
------------+-----------------------------------
      Total |        764      100.00

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