Frequencies for haz_id variable in vehnit dataset :

  HAZARDOUS |
MATERIAL-ID |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      1,326       99.85       99.85
        306 |          1        0.08       99.92
       1977 |          1        0.08      100.00
------------+-----------------------------------
      Total |      1,328      100.00

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