Frequencies for first 10,000 rows of prov2020 variable in pos1991 dataset :

        900 |
cytogenetic |
          s |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      8,536       85.36       85.36
          N |      1,460       14.60       99.96
          Y |          4        0.04      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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