Frequencies for first 10,000 rows of usetobac variable in namcs2012 dataset :

Tobacco Use |      Freq.     Percent        Cum.
------------+-----------------------------------
      Blank |        312        3.12        3.12
    Unknown |      2,449       24.49       27.61
Not current |      6,466       64.66       92.27
    Current |        773        7.73      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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