Frequencies for first 10,000 rows of f_uca_anen variable in natl2010 dataset :

Anencephalu |
          s |
 (uca_anen) |
        U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |          2        0.02        0.02
          1 |      9,998       99.98      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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