Frequencies for first 10,000 rows of prov1970 variable in pos1993 dataset :

        500 |
immunohemat |
      ology |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      8,797       87.97       87.97
          N |      1,156       11.56       99.53
          Y |         47        0.47      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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