Frequencies for drgvers variable in drg1990 dataset :

DRG Version |
 -- FY 1984 |
seems to be |
  Version 1 |      Freq.     Percent        Cum.
------------+-----------------------------------
          7 |        478      100.00      100.00
------------+-----------------------------------
      Total |        478      100.00

by Jean Roth , jroth@nber.org , 22 Apr 2016