Frequencies for first 10,000 rows of prov1975 variable in pos1991 dataset :

510   abo + |
   rh group |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      8,536       85.36       85.36
          N |      1,056       10.56       95.92
          Y |        408        4.08      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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