Disclaimer. Don't rely on these old notes in lieu of reading the literature, but they can jog your memory. As a grad student long ago, my peers and I collaborated to write and exchange summaries of political science research. I posted them to a wiki-style website. "Wikisum" is now dead but archived here. I cannot vouch for these notes' accuracy, nor can I even say who wrote them. If you have more recent summaries to add to this collection, send them my way I guess. Sorry for the ads; they cover the costs of keeping this online.
Eyestone. 1977. Confusion, diffusion, and innovation. APSR 71:441-447.
Directs a few general comments at Gray (who, oddly enough, teaches at the same university--Minnesota). The main contribution is the "Which Policy is Which" section. A smart discussion, but not much empirics.
Gray treats states as identical and interchangable, and assumes that her interactive variable's significance implies actual influence of one state on another. However, it's possible to observe interaction without influence and noninteraction with influence (see 441-442 for examples). Moreover, Gray has tossed out Walker's notion of regional emulation, assuming that any one state might emulate any other. Perhaps if she had considered these competing factors, then she would have noticed that rapidly diffusing policies were generally noninteractive but slowly diffusing policies were generally interactive (Table 1).
Many of the policies Gray studies took over 30 years to diffuse. But a lot happens in 30 years. Can we really assume that states adopt a policy in 1950 for the same reasons that other states adopted it in 1910? We must either restrict our attention to rapidly diffusing policies or look only at the earliest adopters, especially when the policy being adopted was stimulated by an external stimulus (e.g. federal initiatives).
It's hard to classify policies. For example, were fair work laws based on labor or civil rights motivations? Eyestone contends that we can solve this dilemma (Y) by looking at similarities in diffusion trends. If two policies are adopted in roughly the same sequence at roughly the same time across several states, we may conclude that they are being pushed by similar coalitions. "The more similar two policies are, the more similar should be a given state's response to them" (p 444). To use this technique, the two policies must begin their diffusion simultaneously. "If the two policies being compared are in fact similar and simultaneously available for diffusion, they shoul ddiffuse among the states in roughly similar order whether interaction effects are present or not" (p 444).
Research on similar subjects