Frequencies for first 10,000 rows of uca_downs variable in natl2008 dataset :

       Down |
   Syndrome |
        RFP |
771=f_uca_d |
   owns U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          6        0.06        0.06
          2 |      9,991       99.91       99.97
          9 |          3        0.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 May 2016