Frequencies for first 10,000 rows of tracheo variable in natl1990 dataset :

  Tracheo - |
 esophageal |
fistula/Eso |
    phageal |
    atresia |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          2        0.02        0.02
          2 |      9,936       99.36       99.38
          9 |         62        0.62      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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