I found the following pretty useful, albeit its from 2005.
Health insurance for an independent contractor is impossible. This country is in a terrible health insurance situation. We have at least 400,000 songwriters affiliated with the three performing rights organizations who have no coverage at all. These are people that we know don’t have health insurance. It reflects what we’re seeing on a national level in the U.S. Health insurance has just become so expensive for independent contractors; more than half don’t have any health coverage.
Ideally, it would be nice for ASCAP to get group rates, but we would need 70-80 percent of our members to sign up for our health insurance to get group rates. If you don’t do that, you get something that is called “negative selection.” Negative selection means that if you go to any organization and say, “We don’t care if ten or 10,000 of your members sign up. We’ll take any ten or more. If they sign up, fine.” Who signs up? People who can’t get insurance anywhere else. It just blows the whole thing apart. You can’t do that. You need a broad base of people to sign up. We can’t get 70 percent of our members to sign up. Those who really need insurance may have a spouse that has insurance and they’re not going to sign up with us. Or, they can’t afford it, even with a group rate. People who are just starting out of college can’t afford it, for example.
Read more at
http://www.ascap.org/playback/2005/summer/features/musicpro_story.html