Robert J. Landry III (College of Commerce and Business Administration, Jacksonville State University) has posted The Regressivity of Individual State Taxes from 1980 to 2000: A Nationwide Comparison on SSRN.  Here is the abstract:

This study develops a comprehensive measure of individual state tax system burdens for all 50 states. Such an index would be a useful tool to aid policymakers and scholars. Prior comprehensive measures are dated or have not been replicated at regular intervals with the same methodology. Utilizing the representative-taxpayer model, this study develops a comprehensive measure of individual tax system burdens among all 50 states for 1980, 1990 and 2000. From these burdens, a regressivity index across individual state tax systems for each time period is created. This methodology, if replicated at regular intervals, will produce a set of indices which can aid policymakers and scholars conducting empirical research.