Frequencies for first 10,000 rows of notobac variable in nhamcsopd2006 dataset :

       if 'not |
      current' |
   checked for |
  tobacco use, |
      never or |
       former? |      Freq.     Percent        Cum.
---------------+-----------------------------------
         Never |      3,694       36.94       36.94
        Former |        706        7.06       44.00
Not applicable |      4,615       46.15       90.15
         Blank |        985        9.85      100.00
---------------+-----------------------------------
         Total |     10,000      100.00

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