Frequencies for first 10,000 rows of f_uca_down variable in linkpe2013usnum dataset :

       Down |
 Syndrome U |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |          5        0.05        0.05
          1 |      9,995       99.95      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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