A group of interdisciplinary scholars (from Northwestern, the University of Hawaii, and the University of Wisconsin) a have recently collected, refined, and published a 26-year dataset of medical liability insurance premiums on SSRN. Medical Liability Insurance Premia 1990-2015: Dataset, Literature Review, and Summary Information. This paper, and its accompanying Appendix, Codebook, Dataset, and Code are available for download for free.
The researchers, led by Bernard Black of the Northwestern University School of Law and the Kellogg School of Management, state in the abstract that "We hope that the availability of this cleaned dataset will prompt further research on the effects of med mal premiums on provider behavior." I have no doubt that it will. Just looking at the data (and articles cited within), it appears to be a great resource for scholars, lawyers, think-tanks, and legislators when considering issues of medical liability insurance, insurance rates across states, and the impact of tort reform (specifically, statutory caps on economic damages) on liability insurance premiums.