Frequencies for first 10,000 rows of uca_anen variable in natlterr2007 dataset :

Anencephalu |
      s RFP |
752=f_uca_a |
    nen U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          4        0.04        0.04
          2 |      8,684       86.84       86.88
          9 |      1,312       13.12      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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