Frequencies for first 10,000 rows of ven30m variable in natl1996 dataset :

   Assisted |
ventilation |
       - 30 |
 minutes or |
       more |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        141        1.41        1.41
          2 |      9,765       97.65       99.06
          9 |         94        0.94      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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