Frequencies for first 10,000 rows of fed_aid variable in accident dataset :

Federal-Aid |
     System |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      1,207       12.07       12.07
          2 |      2,909       29.09       41.16
          3 |      2,620       26.20       67.36
          4 |        964        9.64       77.00
          5 |      2,299       22.99       99.99
          9 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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