Frequencies for first 10,000 rows of hour variable in person dataset :

 crash time |
     (hour) |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |        403        4.03        4.03
          1 |        311        3.11        7.14
          2 |        380        3.80       10.94
          3 |        221        2.21       13.15
          4 |        254        2.54       15.69
          5 |        307        3.07       18.76
          6 |        333        3.33       22.09
          7 |        368        3.68       25.77
          8 |        265        2.65       28.42
          9 |        256        2.56       30.98
         10 |        268        2.68       33.66
         11 |        354        3.54       37.20
         12 |        452        4.52       41.72
         13 |        396        3.96       45.68
         14 |        433        4.33       50.01
         15 |        470        4.70       54.71
         16 |        481        4.81       59.52
         17 |        701        7.01       66.53
         18 |        725        7.25       73.78
         19 |        575        5.75       79.53
         20 |        542        5.42       84.95
         21 |        509        5.09       90.04
         22 |        505        5.05       95.09
         23 |        398        3.98       99.07
         99 |         93        0.93      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Oct 2016