Frequencies for first 10,000 rows of prov1970 variable in pos1991 dataset :

        500 |
immunohemat |
      ology |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      8,536       85.36       85.36
          N |      1,410       14.10       99.46
          Y |         54        0.54      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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