Frequencies for first 10,000 rows of workrel variable in nhamcsopd1996 dataset :

             is injury work related? |      Freq.     Percent        Cum.
-------------------------------------+-----------------------------------
Not applicable (not an injury visit) |      9,041       90.41       90.41
                                 Yes |         87        0.87       91.28
                                  No |        271        2.71       93.99
                             Unknown |        601        6.01      100.00
-------------------------------------+-----------------------------------
                               Total |     10,000      100.00

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