Frequencies for phaz_id variable in parkwork dataset :

  Hazardous |
  Materials |
Involvement |
  /Placard- |
        HM3 |
Identificat |
 ion Number |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      1,061       99.72       99.72
       1866 |          1        0.09       99.81
       2922 |          1        0.09       99.91
       8888 |          1        0.09      100.00
------------+-----------------------------------
      Total |      1,064      100.00

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