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

SPEED LIMIT |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |         28        0.28        0.28
          5 |          2        0.02        0.30
         10 |          4        0.04        0.34
         15 |         16        0.16        0.50
         20 |         24        0.24        0.74
         25 |        506        5.06        5.80
         30 |        493        4.93       10.73
         35 |      1,082       10.82       21.55
         40 |        917        9.17       30.72
         45 |      1,627       16.27       46.99
         50 |        514        5.14       52.13
         55 |      2,579       25.79       77.92
         60 |        124        1.24       79.16
         65 |      1,052       10.52       89.68
         70 |        633        6.33       96.01
         75 |        174        1.74       97.75
         99 |        225        2.25      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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