Ronen Avraham (Northwestern) undertook the Herculean task of cataloguing state tort law reforms for all fifty states (and DC) during the recent decades. His effort produced "the most detailed, complete and comprehensive dataset of tort reforms in the US." An excerpted abstract follows.
"For each reform we record the effective date, a short description of the reform, whether or not the jury is allowed to know about the reform, whether the reform was upheld or stuck down by the states' supreme courts, as well as whether it was amended by the state legislator."
To be sure, even with such a helpful data source scholars endeavoring to assess the impact of a particular tort reform will necessarily have to addresses such questions as lagging. That said and other technical research design questions aside, Ronen's effort will undoubtedly assist such efforts. Finally, one warning for those desiring to download the paper: at 1,048 pages it is incredibly long (given the task, however, necessarily so).