Frequencies for first 10,000 rows of vbac variable in natl1994 dataset :

    Vaginal |
Birth after |
   previous |
  C-section |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        225        2.25        2.25
          2 |      9,753       97.53       99.78
          9 |         22        0.22      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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