Frequencies for impacts variable in vehicle dataset :

    VEHICLE |
       ROLE |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |         30        4.19        4.19
          1 |        549       76.68       80.87
          2 |        118       16.48       97.35
          3 |         19        2.65      100.00
------------+-----------------------------------
      Total |        716      100.00

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