Frequencies for first 10,000 rows of seen72 variable in nhamcsed2012 dataset :

Has patient |
  been seen |
 in this ED |
 within the |
    last 72 |
  hours and |
discharged? |      Freq.     Percent        Cum.
------------+-----------------------------------
      Blank |        168        1.68        1.68
    Unknown |        878        8.78       10.46
        Yes |        415        4.15       14.61
         No |      8,539       85.39      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 7 Nov 2016