Frequencies for haz_inv variable in vehnit dataset :

  HAZARDOUS |
   MATERIAL |
INVOLVEMENT |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      1,115       99.91       99.91
          2 |          1        0.09      100.00
------------+-----------------------------------
      Total |      1,116      100.00

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