Karen Smith Conway (Department of Economics, University of New Hampshire) & Jonathan C. Rork (Department of Economics, Vassar College) have published State "Death" Taxes and Elderly Migration—The Chicken or the Egg?, 59 Nat’l Tax J. 97 (2006).  Here is the abstract:

Researchers and practitioners hypothesize that the elderly may move to avoid paying “death” (estate, inheritance and gift, or EIG) taxes. Past research on elderly migration, however, has been based on cross–sectional data. Cross–sectional analyses may be misleading as many states that are historical net–importers of the elderly were also among the first to reduce or eliminate their EIG taxes. Using time variability in migration patterns and EIG tax policies and using the young as a "control" group eliminates any evidence that EIG policies affect elderly migration. Rather, we provide evidence that the causality may instead run in the other direction.