Frequencies for first 10,000 rows of uca_downs variable in natlterr2011 dataset :

       Down |
   Syndrome |
        RFP |
771=f_uca_d |
   owns U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          7        0.07        0.07
          2 |      7,636       76.36       76.43
          9 |      2,357       23.57      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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