Here is an article that does provide some interesting evidence about resident choices. The research, by Michelle M. Mello, JD, PhD and Carly N. Kelly, JD both from the Harvard School of Public Health (note the academic degrees), is in a journal I am not normally prone to read (Obstetrics & Gynecology), but due to the ubiquitous SSRN my horizons are being expanded daily.
I don't have access to the full paper, so a can not make a fair critique, but essentially the authors did a survey of medical residents and their program directors in Pennsylvania in 2003. One-third of the residents said they were likely to leave the state due to availability and affordability of med mal cover. Now, this is somewhat incomplete information as one would really want to know if people actually left due to increased med mal prices rather than what they were thinking about when responding to a survey question. However, the med mal insurance problem was cited three times more than any other issue as a reason to leave.
What lends credibility to the study even given my mild criticism is that the residency program directors reported a decrease in residency retention since the onset of the state's liability crisis. Many wonder where doctors move or if they leave the state at all. Evidence of established physicians moving to another state is somewhat anecdotal (see Jon Klick and Thomas Stratmann's paper for a counter example), but what may be easier to see is that young doctors just starting their practice are the least likely to be tied to a practice or a community. So they are more likely to make choices based upon the medical malpractice environment. So rather than seeing changes in established physicians' practices, we see the locational choices being made by the new generation of physicians. This has a long run (rather than an immediate effect) on the stock of physicians in a state. Thus, the longer a state takes to deal with its crises (assuming it has one), the greater will be the potential reduction in the long run stock of physicians in the state.