Frequencies for first 10,000 rows of mddo variable in namcs2008 dataset :

                   md or do |      Freq.     Percent        Cum.
----------------------------+-----------------------------------
  m.d. - doctor of medicine |      8,139       81.39       81.39
d.o. - doctor of osteopathy |      1,861       18.61      100.00
----------------------------+-----------------------------------
                      Total |     10,000      100.00

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