Frequencies for first 10,000 rows of prov1970 variable in pos1995 dataset :

        500 |
immunohemat |
      ology |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      8,884       88.84       88.84
          N |      1,071       10.71       99.55
          Y |         45        0.45      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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