Frequencies for first 10,000 rows of cause33d variable in nhamcsopd2004 dataset :

             cause of injury #3 - broad |      Freq.     Percent        Cum.
----------------------------------------+-----------------------------------
                   not applicable/blank |      9,996       99.96       99.96
                    place of occurrence |          3        0.03       99.99
      central nervous system stimulants |          1        0.01      100.00
----------------------------------------+-----------------------------------
                                  Total |     10,000      100.00

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