Frequencies for start_date variable in hqi_op_procedure_volume dataset :

 Start Date |      Freq.     Percent        Cum.
------------+-----------------------------------
  01jan2012 |      4,124      100.00      100.00
------------+-----------------------------------
      Total |      4,124      100.00

by Jean Roth , jroth@nber.org , 16 Nov 2016