Physician strikes in the United States have been relatively rare, although this has not been the case in other countries nor with other members of the healthcare community, such as nurses. This situation, however, could change. More physicians are either joining unions or seriously discussing doing so. The National Guild for Medical Providers, for example, is actively trying to expand its membership of 11,000 doctors in Michigan, Pennsylvania, and New Hampshire into Illinois, California, New Jersey, Colorado, Texas, and South Carolina. The Federation of Physicians and Dentists, with 2,500 members in Florida and Connecticut, is trying to establish itself in Seattle, Las Vegas, Tucson, and Philadelphia. Although unions are neither necessary nor sufficient conditions for strikes, if physician unions do become more prevalent, the potential for collective work actions, including strikes, increases.