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

Federal-Aid |
     System |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      1,199       11.99       11.99
          2 |      3,077       30.77       42.76
          3 |      2,477       24.77       67.53
          4 |        943        9.43       76.96
          5 |      2,300       23.00       99.96
          9 |          4        0.04      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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