Frequencies for first 10,000 rows of mddo variable in namcs1999 dataset :

   type of physician (md or |
                        do) |      Freq.     Percent        Cum.
----------------------------+-----------------------------------
  M.D. - Doctor of Medicine |      9,184       91.84       91.84
D.O. - Doctor of Osteopathy |        816        8.16      100.00
----------------------------+-----------------------------------
                      Total |     10,000      100.00

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