Frequencies for first 10,000 rows of ca_anen variable in natlterr2009 dataset :

Anencephaly |
        RFP |
635=f_ca_an |
       en R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      2,449       24.49       24.49
          N |      7,549       75.49       99.98
          U |          2        0.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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