This is an important book for students of public policy, federalism, and state politics. Its contribution is to deepen, rather than broaden, our understanding about important and neglected aspects of policy diffusion which is the process by which policies adopted in one jurisdiction spread and change in adoptions in other places. Andrew Karch's study will make us think differently—in a more nuanced way—about policy diffusion: he draws our attention to the different stages on the way to a diffusing policy becoming adopted, and how different sets of factors come into play at the various stages.

After laying out his plan for the book and the rudiments of his conceptual approach, Karch begins his analyses by following the archetype diffusion study. That is to pick a policy or policies and go back in time and across states to see how the policies fared and what factors statistically account for variations in their fate. This book examines five policies: senior prescription drug benefits (1975–2001), Medical Saving Accounts (1993–97), Individual Development Accounts (1993–2001), term limits for those on welfare (1993–96), and family caps on benefits for recipients who have children while on the welfare (1992–98). Applying event history analysis of policy adoption to his five policies, which is the general mode for diffusion studies, Karch finds that the explanatory factors that he calls “the usual suspects” (national intervention, problem severity, state income, legislative professionalism, and state ideology) have at best a middling performance in accounting for the patterns of adoption of his five policies.

So accepting that existing models do not do a very good job of accounting for the adoption of his five policies, Karch moves on to examine different factors and their relative influence at different stages in a “process oriented” approach. The stages he examines in successive chapters are agenda setting (how legislators become aware of the policy proposals), information generation (how legislators learn about the policy and the political outcomes of previous adoptions), and customization (amendments to existing proposals and which the literature calls “reinvention”). His analysis beyond the initial event history models involves qualitative in-depth case studies in three states, Massachusetts, Virginia and Oregon. His evidence consists largely of documentary materials garnered from newspaper accounts, interest groups, think tanks, administrative records, committee hearing and campaign finance data.

The analysis is motivated by an informal theory which centers on reelection-minded legislators who desire solid policy and political information about proposals, but who also operate under severe time constraints. The argument is that they use the best available information that comes in a form that they can use efficiently rather than some theoretically optimal information search, and that reelection as well as the desire to solve problems motivates their use of receptiveness to policy information. In sum he reports that the national government is a major actor in the agenda setting stage, although there is evidence of state initiators active in setting the agendas as well. At the information generation stage Karch assesses the quality of information from a variety of sources including the media, administration reports and studies, and material provided by professional association (interest groups) and think tanks. The latter two produce the kind of information in format and detail that is most useful in evaluating whether to pursue a policy initiative. Although not intended as such, his analysis here provides wonderful teaching examples of how interest groups contribute to and improve legislative policy making. The analysis here is especially innovative and persuasive even though the data does not permit Karch to show direct links between specific information providers and legislators' policy actions.

The relative importance of actors shifts at the customization phase. Here is where legislators craft legislation they believe will work, or even fly politically, in their immediate circumstances. Karch examines who testifies before committees and who contributes to election campaigns, and he finds, consistent with the logic of his theory, that intra-state actors hold sway. These include state chapters of national groups, intrastate groups and state and local government agencies. The national organizations which are important for supplying initial information about the proposals do not have the clout of intrastate groups when it comes to making adjustments so an existing policy proposal.

All of Karch's policies fall into the health and welfare area. These areas have lots of well-organized professionals, and the policies are redistributive and hence among the most publically salient of the policies state legislatures deal with. Without doubting Karch's conclusions for the policies he examines—and he does not make grander claims—further research is necessary to determine if the same dynamics apply to more publicly obscure areas like regulatory policy, budgeting, governmental reorganization or the environment. The positive thing about this book is that it provides a clear logic in thinking about the process as well as a model for analyses of the stages of diffusion. Throughout, its conclusions consistently square with the data presented.

One might think that traipsing sequentially through four policy stages in each of three states would make for a tedious read. Not here. The author has done an admirable job of providing the theoretical rationale for his analyses and enough detail from the individual states to make the case without drowning the reader in excessive description.

My only reservation is the relatively minor role given to legislators and legislatures. Beyond assumptions about reelection motivations and time constraints, they are pretty passive actors in Karch's explanation of diffusion. This is at odds with much current legislative scholarship which focuses on the internal dynamics of the legislative process, including the inter-relationships of preferences, partisanship, position within the legislature and legislative procedures. I do not believe that allowing a role for legislators' preferences and legislative procedures would alter Karch's conclusions, but it would provide a deeper understanding of why policies are chosen for attention, and what information is favored in the development of policy proposals in different legislative settings.

This reservation pales in comparison to the book's strengths. It is a major contribution in providing a nuanced view of the complexity of policy diffusion. It will change the way diffusion and state policy more generally are studied. It is a “must read” for students of state politics, policy diffusion and federalism. Fortunately it is a highly accessible book, ideal for graduate seminars and for upper division classes.