Frequencies for first 10,000 rows of ca_anen variable in natlterr2011 dataset :

Anencephaly |
        RFP |
635=f_ca_an |
       en R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      2,536       25.36       25.36
          N |      6,368       63.68       89.04
          U |      1,096       10.96      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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