Frequencies for first 10,000 rows of prov1910 variable in pos1993 dataset :

        140 |
   virology |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      8,797       87.97       87.97
          N |      1,073       10.73       98.70
          Y |        130        1.30      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 26 Jan 2016