Frequencies for first 10,000 rows of hivser variable in nhamcsed2006 dataset :

        hiv |
   serology |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      9,991       99.91       99.91
        yes |          9        0.09      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016