Frequencies for first_mo variable in vehnit dataset :

      FIRST |
ACCIDENT-MO |
        NTH |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |          3        0.20        0.20
          5 |          1        0.07        0.27
          7 |          2        0.14        0.41
          8 |          2        0.14        0.54
          9 |          1        0.07        0.61
         99 |      1,472       99.39      100.00
------------+-----------------------------------
      Total |      1,481      100.00

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