Frequencies for first 10,000 rows of anen variable in natlterr2000 dataset :

Anencephalu |
          s |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          1        0.01        0.01
          2 |      9,990       99.90       99.91
          9 |          9        0.09      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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