Frequencies for first 10,000 rows of mddo variable in namcs2013 dataset :

  Type of doctor (MD or DO) |      Freq.     Percent        Cum.
----------------------------+-----------------------------------
  M.D. - Doctor of Medicine |      9,388       93.88       93.88
D.O. - Doctor of Osteopathy |        612        6.12      100.00
----------------------------+-----------------------------------
                      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 27 Mar 2017