Frequencies for first 10,000 rows of vbac variable in natl1989 dataset :

    Vaginal |
Birth after |
   previous |
  C-section |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        112        1.12        1.12
          2 |      9,829       98.29       99.41
          9 |         59        0.59      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 Jan 2016