Frequencies for first 10,000 rows of f_ob_succ variable in natl2009 dataset :

 Successful |
   External |
   Cephalic |
    Version |
(op_ecvs) R |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,933       99.33       99.33
          1 |         67        0.67      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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