Frequencies for first 10,000 rows of injury72 variable in nhamcsed2014 dataset :

    Did the injury/trauma, |
    overdose, or poisoning |
     occur within 72 hours |
              prior to the |      Freq.     Percent        Cum.
---------------------------+-----------------------------------
                     Blank |      7,722       77.22       77.22
                   Unknown |        106        1.06       78.28
                       Yes |      1,832       18.32       96.60
                        No |        326        3.26       99.86
Questionable injury status |         14        0.14      100.00
---------------------------+-----------------------------------
                     Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 11 Apr 2017