Frequencies for first 10,000 rows of vbac variable in natl2000 dataset :

    Vaginal |
Birth after |
   previous |
  C-section |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        158        1.58        1.58
          2 |      9,802       98.02       99.60
          9 |         40        0.40      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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