Frequencies for first 10,000 rows of retref variable in nhamcsed2004 dataset :

  return to |
  referring |
  physician |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      8,449       84.49       84.49
        yes |      1,551       15.51      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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