Frequencies for first 10,000 rows of usetobac variable in namcs2009 dataset :

tobacco use |      Freq.     Percent        Cum.
------------+-----------------------------------
      blank |        368        3.68        3.68
    unknown |      2,366       23.66       27.34
not current |      6,288       62.88       90.22
    current |        978        9.78      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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