Frequencies for first 10,000 rows of hivser variable in nhamcsed1995 dataset :

        hiv |
   serology |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,982       99.82       99.82
          1 |         18        0.18      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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