Frequencies for first 10,000 rows of vbac variable in linkco1991us_num dataset :

    Vaginal |
Birth After |
   previous |
  C-section |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        160        1.60        1.60
          2 |      9,696       96.96       98.56
          9 |        144        1.44      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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