Frequencies for first 10,000 rows of uca_anen variable in natl2011 dataset :

Anencephalu |
      s RFP |
752=f_uca_a |
    nen U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          1        0.01        0.01
          2 |      7,802       78.02       78.03
          9 |      2,197       21.97      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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