Frequencies for first 10,000 rows of haz_id variable in vehicle dataset :

  Hazardous |
  Materials |
Involvement |
  /Placard- |
        HM3 |
Identificat |
 ion Number |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,974       99.74       99.74
       1072 |          1        0.01       99.75
       1075 |          1        0.01       99.76
       1077 |          1        0.01       99.77
       1203 |          8        0.08       99.85
       1219 |          1        0.01       99.86
       1267 |          2        0.02       99.88
       1268 |          1        0.01       99.89
       1824 |          1        0.01       99.90
       1830 |          1        0.01       99.91
       1993 |          1        0.01       99.92
       3077 |          1        0.01       99.93
       8888 |          6        0.06       99.99
       9999 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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