You might want to read the references you use.....
Checking your own reference: Seventy graduates (55%) practice EM only, 47 graduates (37%) practice both EM and IM, and nine graduates (7%) practice IM or an IM subspecialty only. Numbers are copied and pasted. Your number 64% are those that believe it practical to practice both EM and IM. Meaning up to 36% of EM/IM graduates agree that it is NOT practical to practice both at all.
http://www.ncbi.nlm.nih.gov/pubmed/19673705
So only approximately 1/3 use both. Of those that use both, I can't tell what percentage of their time is dedicated to each. I doubt it is near 50/50 because of financial reasons...., but I'm only looking at the abstract.
My common sense seems to hold up with your help........don't need my own references......