Frequencies for first 10,000 rows of lung variable in natl1994 dataset :

   Acute or |
    chronic |
       lung |
    disease |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          9        0.09        0.09
          2 |      9,944       99.44       99.53
          9 |         47        0.47      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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