Frequencies for first 10,000 rows of ca_downs variable in natl2014 dataset :

       Down |
 Syndrome C |
  Confirmed |      Freq.     Percent        Cum.
------------+-----------------------------------
          C |          1        0.01        0.01
          N |      9,997       99.97       99.98
          P |          2        0.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 15 Jun 2016