Frequencies for first 10,000 rows of ip_chlam variable in natl2015 dataset :

Chlamydia Y |
        Yes |      Freq.     Percent        Cum.
------------+-----------------------------------
          N |      9,602       96.02       96.02
          U |        128        1.28       97.30
          Y |        270        2.70      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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