Frequencies for first 10,000 rows of workrel variable in nhamcsed2000 dataset :

             is injury work related? |      Freq.     Percent        Cum.
-------------------------------------+-----------------------------------
                                 Yes |        374        3.74        3.74
                                  No |      2,081       20.81       24.55
                             Unknown |      1,176       11.76       36.31
Not applicable (not an injury visit) |      6,369       63.69      100.00
-------------------------------------+-----------------------------------
                               Total |     10,000      100.00

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