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

Federal-Aid |
     System |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      1,127       11.27       11.27
          2 |      3,072       30.72       41.99
          3 |      2,457       24.57       66.56
          4 |      1,032       10.32       76.88
          5 |      2,306       23.06       99.94
          9 |          6        0.06      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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