http://asclepion.blogspot.com/2015/07/the-job-hunt-ii-geographic-variations.html
"Nevertheless, because of family, friends, our social network, our fear of inclement weather, our personal desires and goals, or any dozen other reasons, we tend to stay in the place we did our training, and often, that means in places that are replete with physicians. The Bay Area, for example, is a tight market. When I first started sending out letters of inquiry, half of my emails got no response, and a quarter got a "Thank you for your interest, but we're not looking to hire." Only a few groups were actively and publicly recruiting; most were only looking around through contacts or not necessarily in need of another doctor.
Thus, all my colleagues in the Bay Area felt intense pressure if they wanted to stay. In fact, more than half my residency and nearly 90% of my fellowship class ended up leaving this area because there simply weren't acceptable jobs. This can be really scary, and it's why even for a well-trained highly qualified physician, finding a job isn't a walk in the park."