Frequencies for first 10,000 rows of uca_anen variable in natl2008 dataset :

Anencephalu |
      s RFP |
752=f_uca_a |
    nen U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          2        0.02        0.02
          2 |      9,995       99.95       99.97
          9 |          3        0.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 May 2016