Frequencies for first 10,000 rows of uca_downs variable in natl2011 dataset :

       Down |
   Syndrome |
        RFP |
771=f_uca_d |
   owns U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          3        0.03        0.03
          2 |      7,800       78.00       78.03
          9 |      2,197       21.97      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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