Frequencies for first 10,000 rows of f_uca_anen variable in natl2004 dataset :

Anencephalu |
        s U |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |          4        0.04        0.04
          1 |      9,996       99.96      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 21 Jan 2016