Frequencies for first 10,000 rows of ca_downs variable in natlterr2015 dataset :

       Down |
 Syndrome C |
  Confirmed |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      1,078       10.78       10.78
          N |      8,803       88.03       98.81
          P |          5        0.05       98.86
          U |        114        1.14      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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