Frequencies for first 10,000 rows of ab_aven1 variable in natlterr2014 dataset 

   Assisted |
Ventilation |
(immediatel |
   y) Y Yes |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      1,077       10.77       10.77
          N |      8,686       86.86       97.63
          U |         98        0.98       98.61
          Y |        139        1.39      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 15 Jun 2016