Frequencies for first 10,000 rows of workrel variable in nhamcsed1997 dataset :

             is injury work related? |      Freq.     Percent        Cum.
-------------------------------------+-----------------------------------
                                 Yes |        389        3.89        3.89
                                  No |      2,209       22.09       25.98
                             Unknown |      1,079       10.79       36.77
Not applicable (not an injury visit) |      6,323       63.23      100.00
-------------------------------------+-----------------------------------
                               Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016