Innovations that served as the basis for this study were collected using the following protocol: To ensure a balanced representation of state public policies by historical era, policy type, and speed of diffusion, this research followed the sampling procedures proposed by Walker (1969) and Savage (1978), sampling from a discrete list of state issue areas representing welfare, health and public safety, crime and corrections, taxes, licensing and professional regulation, education, elections, sexuality, state economic development, and environmental policy. Following Walker's definition of innovation as “a program or policy which is new to the state adopting it, no matter how old the program may be or how many other states have adopted it,”(1969, 881), this research included only innovations that were formally enacted into law by state governmental institutions. In keeping with common selection criteria in innovation and diffusion research, the scope of innovation adoption was considered for identifying diffusing innovations (Walker 1969; Savage 1978; Canon and Baum 1981). Only those innovations adopted by at least 10 states before 2007 were included for analysis.

Below are two lists of innovations that served as the basis for this study. The first list represents innovations provided from data compiled by Jack Walker for his study “The Diffusion of Public Policy Innovation Among the American States” (1972).