“While it is too early to make a definitive connection, it appears that the regulation encourages young adults to switch from obtaining coverage on their own, where they will pay additional costs, to obtaining coverage as dependents, where parents and parents’ employers will foot the bill. The regulation hence simply shifts costs from one group of people (young adults) to another (their parents and parents’ employers). This sort of distortion contributes to increases in premiums that the Administration expects in response to the regulation.”