Frequencies for first 10,000 rows of workrel variable in nhamcsed2002 dataset :

             is injury work related? |      Freq.     Percent        Cum.
-------------------------------------+-----------------------------------
                                 Yes |        255        2.55        2.55
                                  No |      1,999       19.99       22.54
                             Unknown |      1,251       12.51       35.05
Not applicable (not an injury visit) |      6,495       64.95      100.00
-------------------------------------+-----------------------------------
                               Total |     10,000      100.00

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