It's hard to say. There are about nine programs, each taking two residents/year (except christiana -- 3, and downstate ny -- ?6?); at one program last year, between 80-100 applications were received for the two spots.
I don't know what that means. When I applied, I applied to most of the combined programs, and used emergency med programs as backup (some combined people used im as backup). I applied to enough programs to get 10-15 interviews total.
I think that the question, although valid, shouldn't change your strategy for application. If you want to be im/em, apply for it, and apply backup, regardless of how competitive you feel your application will be.
That being said, it is MAJORLY self-selective. Most people DON'T want to do it because it involves five years. And because em folk generally don't like rounding/having a beeper/Eternal medicine..