Frequencies for first 10,000 rows of ob_ecvf variable in natlterr2014 dataset :

     Failed |
   External |
   Cephalic |
  Version Y |
        Yes |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      1,077       10.77       10.77
          N |      8,766       87.66       98.43
          U |        149        1.49       99.92
          Y |          8        0.08      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 15 Jun 2016