Frequencies for first 10,000 rows of uca_anen variable in natlterr2006 dataset :

Anencephalu |
      s RFP |
752=f_uca_a |
    nen U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          1        0.01        0.01
          2 |      8,508       85.08       85.09
          9 |      1,491       14.91      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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