Frequencies for haz_carg variable in vehicle dataset :

  HAZARDOUS |
      CARGO |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |        574       91.69       91.69
          9 |         52        8.31      100.00
------------+-----------------------------------
      Total |        626      100.00

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