Frequencies for first 10,000 rows of workrel variable in nhamcsopd1998 dataset :

             is injury work related? |      Freq.     Percent        Cum.
-------------------------------------+-----------------------------------
                                 Yes |         95        0.95        0.95
                                  No |        325        3.25        4.20
                             Unknown |        455        4.55        8.75
Not applicable (not an injury visit) |      9,125       91.25      100.00
-------------------------------------+-----------------------------------
                               Total |     10,000      100.00

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