Frequencies for impacts variable in vehicle dataset :

    VEHICLE |
       ROLE |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |         20        3.68        3.68
          1 |        366       67.28       70.96
          2 |        140       25.74       96.69
          3 |         18        3.31      100.00
------------+-----------------------------------
      Total |        544      100.00

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