Frequencies for first 10,000 rows of workrel variable in namcs2000 dataset :

             is injury work related? |      Freq.     Percent        Cum.
-------------------------------------+-----------------------------------
                                 Yes |        168        1.68        1.68
                                  No |        300        3.00        4.68
                             Unknown |        531        5.31        9.99
Not applicable (not an injury visit) |      9,001       90.01      100.00
-------------------------------------+-----------------------------------
                               Total |     10,000      100.00

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