Frequencies for first 10,000 rows of vbac variable in natl1999 dataset :

    Vaginal |
Birth after |
   previous |
  C-section |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        240        2.40        2.40
          2 |      9,734       97.34       99.74
          9 |         26        0.26      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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