Frequencies for first 10,000 rows of downs variable in natl2002 dataset :

     Down's |
   syndrome |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          5        0.05        0.05
          2 |      9,580       95.80       95.85
          9 |        415        4.15      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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