Frequencies for first 10,000 rows of refphys variable in nhamcsopd1995 dataset :

  return to |
  referring |
  physician |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,572       95.72       95.72
          1 |        428        4.28      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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