Frequencies for first 10,000 rows of usetobac variable in nhamcsopd2005 dataset :

    tobacco |
   use: not |
   current, |
    current |      Freq.     Percent        Cum.
------------+-----------------------------------
      blank |        386        3.86        3.86
not current |      4,909       49.09       52.95
    current |      1,376       13.76       66.71
    unknown |      3,329       33.29      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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