Frequencies for first 10,000 rows of vbac variable in natl2002 dataset :

    Vaginal |
birth after |
   previous |
  C-section |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        177        1.77        1.77
          2 |      9,802       98.02       99.79
          9 |         21        0.21      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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