Frequencies for first 10,000 rows of usetobac variable in namcs2007 dataset :

tobacco use |      Freq.     Percent        Cum.
------------+-----------------------------------
      blank |        622        6.22        6.22
    unknown |      2,537       25.37       31.59
not current |      5,847       58.47       90.06
    current |        994        9.94      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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