Frequencies for first 10,000 rows of uca_downs variable in natlterr2010 dataset :

       Down |
   Syndrome |
        RFP |
771=f_uca_d |
   owns U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          9        0.09        0.09
          2 |      7,725       77.25       77.34
          9 |      2,266       22.66      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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