Frequencies for first 10,000 rows of lung variable in natl1993 dataset :

   Acute or |
    chronic |
       lung |
    disease |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          6        0.06        0.06
          2 |      9,972       99.72       99.78
          9 |         22        0.22      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015