Frequencies for first 10,000 rows of tracheo variable in linkco1991us_num dataset :

Tracheo-eso |
    phageal |
fistula/Eso |
    phageal |
    atresia |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         24        0.24        0.24
          2 |      9,703       97.03       97.27
          9 |        273        2.73      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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