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

SPEED LIMIT |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |         40        0.40        0.40
          5 |          2        0.02        0.42
         10 |          3        0.03        0.45
         15 |         19        0.19        0.64
         20 |         18        0.18        0.82
         25 |        511        5.11        5.93
         30 |        489        4.89       10.82
         35 |      1,119       11.19       22.01
         40 |        870        8.70       30.71
         45 |      1,599       15.99       46.70
         50 |        517        5.17       51.87
         55 |      2,385       23.85       75.72
         60 |        191        1.91       77.63
         65 |      1,225       12.25       89.88
         70 |        610        6.10       95.98
         75 |        196        1.96       97.94
         99 |        206        2.06      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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