Frequencies for first 10,000 rows of vbac variable in natl1996 dataset :

    Vaginal |
Birth after |
   previous |
  C-section |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        236        2.36        2.36
          2 |      9,751       97.51       99.87
          9 |         13        0.13      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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