Frequencies for first 10,000 rows of ca_downs variable in natl2017 dataset :

       Down |
 Syndrome C |
  Confirmed |      Freq.     Percent        Cum.
------------+-----------------------------------
          C |          6        0.06        0.06
          N |      9,989       99.89       99.95
          P |          5        0.05      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 19 Sep 2018