Frequencies for first 10,000 rows of workrel variable in namcs1997 dataset :

             is injury work related? |      Freq.     Percent        Cum.
-------------------------------------+-----------------------------------
                                 Yes |        174        1.74        1.74
                                  No |        278        2.78        4.52
                             Unknown |        401        4.01        8.53
Not applicable (not an injury visit) |      9,147       91.47      100.00
-------------------------------------+-----------------------------------
                               Total |     10,000      100.00

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