Frequencies for first 10,000 rows of congan variable in natlterr2001 dataset :

 Congenital |
  anomalies |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |         20        0.20        0.20
          1 |      9,980       99.80      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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