Frequencies for first 10,000 rows of congan variable in natlterr1997 dataset :

 Congenital |
  anomalies |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |         17        0.17        0.17
          1 |      9,983       99.83      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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