Frequencies for first 10,000 rows of mddo variable in namcs2007 dataset :

                   md or do |      Freq.     Percent        Cum.
----------------------------+-----------------------------------
  m.d. - doctor of medicine |      7,988       79.88       79.88
d.o. - doctor of osteopathy |      2,012       20.12      100.00
----------------------------+-----------------------------------
                      Total |     10,000      100.00

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