Frequencies for first 10,000 rows of prov1910 variable in pos1995 dataset :

        140 |
   virology |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      8,884       88.84       88.84
          N |        994        9.94       98.78
          Y |        122        1.22      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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