Frequencies for first 10,000 rows of notobac variable in nhamcsopd2005 dataset :

       if 'not |
      current' |
   checked for |
  tobacco use, |
      never or |
       former? |      Freq.     Percent        Cum.
---------------+-----------------------------------
         never |      3,767       37.67       37.67
        former |        725        7.25       44.92
not applicable |      5,091       50.91       95.83
         blank |        417        4.17      100.00
---------------+-----------------------------------
         Total |     10,000      100.00

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