Frequencies for phaz_rel variable in parkwork dataset :

  hazardous |
  materials |
involvement |
/placard-hm |
 5 released |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      1,142       99.65       99.65
          1 |          1        0.09       99.74
          8 |          3        0.26      100.00
------------+-----------------------------------
      Total |      1,146      100.00

by Jean Roth , jroth@nber.org , 22 Oct 2016