Frequencies for first 10,000 rows of mammo variable in namcs2000 dataset :

mammography |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,820       98.20       98.20
          1 |        180        1.80      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016