Frequencies for first 10,000 rows of usetobac variable in namcs2011 dataset :

Tobacco use |      Freq.     Percent        Cum.
------------+-----------------------------------
      Blank |        396        3.96        3.96
    Unknown |      2,162       21.62       25.58
Not current |      6,535       65.35       90.93
    Current |        907        9.07      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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