Frequencies for first 10,000 rows of hivser variable in nhamcsed1993 dataset :

        hiv |
   serology |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,932       99.32       99.32
          1 |         68        0.68      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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