Frequencies for first 10,000 rows of usetobac variable in namcs2013 dataset :

Tobacco Use |      Freq.     Percent        Cum.
------------+-----------------------------------
      Blank |        382        3.82        3.82
    Unknown |      1,784       17.84       21.66
Not current |      6,950       69.50       91.16
    Current |        884        8.84      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 27 Mar 2017