Frequencies for first 10,000 rows of uca_downs variable in natl2015 dataset :

       Down |
 Syndrome 1 |
    Anomaly |
   reported |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          7        0.07        0.07
          2 |      9,992       99.92       99.99
          9 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 20 Oct 2016