Frequencies for first 10,000 rows of ip_syph variable in natl2016 dataset :

 Syphilis Y |
        Yes |      Freq.     Percent        Cum.
------------+-----------------------------------
          N |      9,909       99.09       99.09
          U |         89        0.89       99.98
          Y |          2        0.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 4 Oct 2017