Frequencies for first 10,000 rows of vbac variable in natlterr1999 dataset :

    Vaginal |
Birth after |
   previous |
  C-section |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        104        1.04        1.04
          2 |      9,893       98.93       99.97
          9 |          3        0.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015