Frequencies for first 10,000 rows of seen72 variable in nhamcsed2013 dataset :

Has patient |
  been seen |
 in this ED |
 within the |
    last 72 |
  hours and |
discharged? |      Freq.     Percent        Cum.
------------+-----------------------------------
      Blank |        180        1.80        1.80
    Unknown |        654        6.54        8.34
        Yes |        382        3.82       12.16
         No |      8,784       87.84      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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