Frequencies for first 10,000 rows of uca_downs variable in natl2004 dataset :

       Down |
   Syndrome |
        U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          5        0.05        0.05
          2 |      8,769       87.69       87.74
          9 |      1,226       12.26      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 21 Jan 2016